It is likely an outdated/broken gfx driver, having nothing to do with the monitor. While holding down the SHIFT key, right-click on the DDM system tray icon and select "Save diagnostic report" from the popup menu; then post the content of the report.

Dear Argentum,

Thanks for the suggestion.

As I see no way on the Community Forum to insert files, I will simply paste the report, below.

Hope you'll find something helpful in it.

All the best,

Eric

=========  Report Beginning ==============

Diagnostic Report, generated 13-Nov-20 (10.0.19042)
Copyright (c) 1995-2020, EnTech Taiwan.
Version = 1.51.0.2015
OS = 10.0.19042.2 x64
Mechanism = 3
Account = Standard
Command line = "C:\Program Files (x86)\Dell\Dell Display Manager\ddm.exe"
////////////////////////////////////////
Configuration settings:
DriverError = Dell S2340T=
LastCheck = 0x0000AC6E
HintShown = 0x00000001
AutoRestoreWindowLayout = 0x00000000
GlassBorder.DEL4085.NWGM8332EESL = 0x00000100
AppScan.DEL4085.NWGM8332EESL = 0x00000004
DEL4085 = 0x00000001
FW.DEL4085.NWGM8332EESL = 0x00000003
EApolicy = 2000 2000 2000 2000 2000 2000
EnumErrorCount = 0x00000000
////////////////////////////////////////
19:02:42.169...Log opened
19:02:42.187...WinOS = 19042
19:02:42.262...LanguageID = 00000409 00000409 00000409
19:02:42.281...Build = 1.51.0.2015
19:02:42.282...Windows handles = 0002018E 00010100 00010196
19:02:42.286...OS monitor sleep timeout value = 900 ms.
19:02:42.287...Applied DPI = 96-96
19:02:42.288...VM = 0
19:02:42.289...Registered DDM popup hotkey = Shift+Ctrl+D 6044
19:02:42.290...Registered EA layout MRU hotkey = Shift+Ctrl+Home 6024
19:02:42.293...Registered application window hotkey = Shift+Ctrl+Ins 602D
19:02:42.300...Remote asset management = 1
19:02:42.301...Remote registry service state = 4
19:02:42.571...WMI service state (unless firewalled) = 1
19:02:42.653...DMA = 3
19:02:42.664...Starting enumeration
19:02:42.775...1. DEL4085.NWGM8332EESL on NVIDIA Quadro RTX 4000
19:02:42.777......Monitor assignment = 1
19:02:42.777......Adapter name = \\.\DISPLAY1
19:02:42.778......Monitor name = Dell S2340T (DP)
19:02:42.779......Vendor ID = 10DE
19:02:42.783......GPU driver = c:\windows\system32\driverstore\filerepository\nv_dispwi 27.21.14.5709
19:02:42.784......Flags = 00000005.00000003
19:02:42.786......Display tag = A502A584
19:02:42.787......Monitor handle = 0001008B
19:02:42.788......Monitor screen area = 0,0 x 1920,1080 1920x1080
19:02:42.789......Monitor work area = 0,0 x 1920,1050 1920x1050
19:02:42.790......Monitor scaling factor = 100%
19:02:42.791......Raw EDID = 00FFFFFFFFFFFF0010AC85404C53454509170104A5331D783A6431A35751A2270F5054A54B00714F8180A9C0D1C00101010101010101023A801871382D40582C4500FD1E1100001E000000FF004E57474D383333324545534C0A000000FC0044454C4C205332333430540A20000000FD00384C1E5111010A20202020202001A5
19:02:42.846......VCP10 = 0064004B
19:02:42.849......OS device handle = 0001008B.00000000
19:02:42.853......Capabilities string = (prot(monitor)type(lcd)model(s2340t)cmds(01 02 03 07 0c e3 f3)vcp(02 04 05 06 08 10 12 14(05 08 0b 0c) 16 18 1a 52 60(0f 11) ac ae b2 b6 c8 c9 d6(01 04 05) dc(00 02 03 05) df e0 e1 e2(00 01 02 04 06 0e 12 14) f0(00 01) f1 f2)mswhql(1)asset_eep(40)mccs_ver(2.1)) (cached)
19:02:43.117......Firmware string = M3T003
19:02:43.126......Configuration = FF0003.FF0074.1709
19:02:43.130......Model = Dell S2340T
19:02:43.135......Model year = FY13
19:02:43.138......Opcodes supported = 02,04,05,06,08,10,12,14,16,18,1A,52,60,AC,AE,B2,B6,C8,C9,D6,DC,DF,E0,E1,E2,F0,F1,F2
19:02:43.245......Timing = 67.50 kHz (+), 60.00 Hz (-)
19:02:43.247......Status = 0040001D
19:02:43.580...5. DEL4084.8R33926O00QS on DisplayLink USB Device
19:02:43.581......Monitor assignment = 2
19:02:43.582......Adapter name = \\.\DISPLAY5
19:02:43.583......Monitor name = Dell S2340T (HDMI)
19:02:43.584......Vendor ID = 17E9
19:02:43.585......GPU driver =
19:02:43.586......Flags = 00000001.00000003
19:02:43.587......Display tag = 8A028084
19:02:43.588......Monitor handle = 00020001
19:02:43.588......Monitor screen area = 1920,0 x 3840,1080 1920x1080
19:02:43.589......Monitor work area = 1920,0 x 3840,1050 1920x1050
19:02:43.590......Monitor scaling factor = 100%
19:02:43.591......Raw EDID = 00FFFFFFFFFFFF0010AC8440535130301116010380331D78EA6430A35751A2270F5054A54B00714F8180A9C0D1C00101010101010101023A801871382D40582C4500FD1E1100001E000000FF00385233333932364F303051530A000000FC0044454C4C205332333430540A20000000FD00384C1E5111000A202020202020018A
19:02:43.817......Error: communicating via DDC/CI (0x0000001F) = A device attached to the system is not functioning
19:02:43.819......Error: display driver does not support DDC/CI
19:02:46.567......Error: communicating via DDC/CI (0x0000001F) = A device attached to the system is not functioning
19:02:46.572......Error: display driver does not support DDC/CI
19:02:51.800......Error: communicating via DDC/CI (0x0000001F) = A device attached to the system is not functioning
19:02:51.801......Error: display driver does not support DDC/CI
19:02:51.803......Discarding unsupported display: DEL4084.8R33926O00QS on DisplayLink USB Device
19:02:51.816......Check: monitor and connection to monitor to ensure DDC/CI is supported and enabled
19:02:51.833......Status = 0040001D
19:02:51.835...Ending enumeration
19:02:51.839...New=DEL4085.0003 DEL4084.0004
19:02:51.908...Creating VCP table on DEL4085.NWGM8332EESL
19:02:51.962......Opcode 0x12 = 0064004B
19:02:52.083......Opcode 0x60 = 000F000F
19:02:52.266...Video power down timeout = 900
19:02:52.275...Display powered ON
19:02:52.276...User session connect
19:02:52.299...Auto-saving window layout...
19:16:55.286...User session disconnect
19:28:16.459...Display powered OFF
20:11:35.789...Display powered ON
20:11:35.799...User session connect
20:11:40.863...Refreshing screen object
20:30:03.286...User session disconnect
20:41:18.461...Display powered OFF
22:16:22.137...Display powered ON
22:16:22.198...User session connect
22:16:27.243...Refreshing screen object
22:23:45.708...User session disconnect
22:35:01.885...Display powered OFF
22:38:58.616...Display powered ON
22:38:58.627...User session connect
22:39:03.658...Refreshing screen object
22:59:59.363...User session disconnect
23:08:32.334...User session connect
23:08:37.350...Refreshing screen object
00:00:18.365...User session disconnect
00:08:24.698...User session connect
00:08:29.818...Refreshing screen object
00:40:04.364...User session disconnect
00:51:20.545...Display powered OFF
08:26:03.686...Display powered ON
08:26:03.764...User session connect
08:26:08.810...Refreshing screen object
09:08:02.383...User session disconnect
09:19:18.567...Display powered OFF
15:16:52.489...Display powered ON
15:16:52.542...User session connect
15:16:57.551...Refreshing screen object
15:46:58.086...\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
15:46:58.087...Dump: Windows device enumeration
15:46:58.118...Display adapters:
15:46:58.125.....1.DELL S2340T USB
15:46:58.126.....2.DELL S2340T USB
15:46:58.126.....3.NVIDIA Quadro RTX 4000
15:46:58.127...Monitors:
15:46:58.134.....1.Dell S2340T (DP)
15:46:58.135.....2.Dell S2340T (HDMI)
15:46:58.135...Visible monitors = 2
15:46:58.136...1.DeviceName = \\.\DISPLAY1
15:46:58.137.....DeviceFlags = 00000005
15:46:58.138.....DeviceString = NVIDIA Quadro RTX 4000
15:46:58.139.....DeviceID = PCI\VEN_10DE&DEV_1EB1&SUBSYS_12A010DE&REV_A1
15:46:58.139.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{90862476-A8A7-11EA-BE78-EAC529B4A600}\0000
15:46:58.142.....a.MonitorName = \\.\DISPLAY1\Monitor0
15:46:58.143.......MonitorFlags = 00000003
15:46:58.143.......MonitorString = Dell S2340T (DP)
15:46:58.144.......MonitorID = MONITOR\DEL4085\{4d36e96e-e325-11ce-bfc1-08002be10318}\0003
15:46:58.145.......MonitorKey = \Registry\Machine\System\CurrentControlSet\Control\Class\{4d36e96e-e325-11ce-bfc1-08002be10318}\0003
15:46:58.146.......Raw EDID = 00FFFFFFFFFFFF0010AC85404C53454509170104A5331D783A6431A35751A2270F5054A54B00714F8180A9C0D1C00101010101010101023A801871382D40582C4500FD1E1100001E000000FF004E57474D383333324545534C0A000000FC0044454C4C205332333430540A20000000FD00384C1E5111010A20202020202001A5
15:46:58.147...2.DeviceName = \\.\DISPLAY2
15:46:58.148.....DeviceFlags = 00000000
15:46:58.149.....DeviceString = NVIDIA Quadro RTX 4000
15:46:58.150.....DeviceID = PCI\VEN_10DE&DEV_1EB1&SUBSYS_12A010DE&REV_A1
15:46:58.151.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{90862476-A8A7-11EA-BE78-EAC529B4A600}\0001
15:46:58.154...3.DeviceName = \\.\DISPLAY3
15:46:58.155.....DeviceFlags = 00000000
15:46:58.156.....DeviceString = NVIDIA Quadro RTX 4000
15:46:58.157.....DeviceID = PCI\VEN_10DE&DEV_1EB1&SUBSYS_12A010DE&REV_A1
15:46:58.158.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{90862476-A8A7-11EA-BE78-EAC529B4A600}\0002
15:46:58.159...4.DeviceName = \\.\DISPLAY4
15:46:58.160.....DeviceFlags = 00000000
15:46:58.162.....DeviceString = NVIDIA Quadro RTX 4000
15:46:58.163.....DeviceID = PCI\VEN_10DE&DEV_1EB1&SUBSYS_12A010DE&REV_A1
15:46:58.164.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{90862476-A8A7-11EA-BE78-EAC529B4A600}\0003
15:46:58.166...5.DeviceName = \\.\DISPLAY5
15:46:58.168.....DeviceFlags = 00000001
15:46:58.169.....DeviceString = DisplayLink USB Device
15:46:58.170.....DeviceID = USB\VID_17E9&PID_4312&REV_3122&MI_00
15:46:58.171.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{C30AA74A-2066-11EB-BEA6-380025257A00}\0000
15:46:58.174.....a.MonitorName = \\.\DISPLAY5\Monitor0
15:46:58.175.......MonitorFlags = 00000003
15:46:58.176.......MonitorString = Dell S2340T (HDMI)
15:46:58.177.......MonitorID = MONITOR\DEL4084\{4d36e96e-e325-11ce-bfc1-08002be10318}\0004
15:46:58.178.......MonitorKey = \Registry\Machine\System\CurrentControlSet\Control\Class\{4d36e96e-e325-11ce-bfc1-08002be10318}\0004
15:46:58.179.......Raw EDID = 00FFFFFFFFFFFF0010AC8440535130301116010380331D78EA6430A35751A2270F5054A54B00714F8180A9C0D1C00101010101010101023A801871382D40582C4500FD1E1100001E000000FF00385233333932364F303051530A000000FC0044454C4C205332333430540A20000000FD00384C1E5111000A202020202020018A
15:46:58.180...Total number of monitors enumerated = 2
15:46:58.181...\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
15:46:58.182...Dumping VCP table on DEL4085.NWGM8332EESL
15:46:58.244......Opcode 0x02 = 00020001
15:46:58.363......Opcode 0x10 = 0064004B
15:46:58.483......Opcode 0x12 = 0064004B
15:46:58.604......Opcode 0x14 = 000C0005
15:46:58.724......Opcode 0x16 = 00640064
15:46:58.844......Opcode 0x18 = 00640064
15:46:58.964......Opcode 0x1A = 00640064
15:46:59.085......Opcode 0x52 = 00FF0000
15:46:59.204......Opcode 0x60 = 000F000F
15:46:59.324......Opcode 0xAC = 000107AC
15:46:59.445......Opcode 0xAE = FFFF1766
15:46:59.565......Opcode 0xB2 = 00010001
15:46:59.686......Opcode 0xB6 = 00050003
15:46:59.806......Opcode 0xC8 = 00247309
15:46:59.925......Opcode 0xC9 = FFFF0003
15:47:00.045......Opcode 0xD6 = 00050001
15:47:00.166......Opcode 0xDC = 00050000
15:47:00.285......Opcode 0xDF = FFFF0201
15:47:00.405......Opcode 0xE2 = 00160000
15:47:00.525......Opcode 0xF0 = 00FF0000
15:47:00.646......Opcode 0xF1 = 00FF0003
15:47:00.766......Opcode 0xF2 = 00FF0000
15:47:00.826......VCP table dumped

========= Report End ================

It does not appear there is anything wrong. You have your monitor connected (a) directly to the NVidia graphics card, which is working, as well as (b) thru USB via the DisplayLink interface, which is not working because of (a) - hence the error message.

It looks like the USB/DisplayLink connection may be a legacy of your old PC, but its not entirely clear how you have things connected physically.

Dear Argentum,

Thanks for the prompt & enlightening input.

Still, the "legacy" thing kind of doesn't add up:

1. Indeed, I had an old PC;
2. However, the PC to which the S2340T is connected now is completely new, built from bare metal, component by component, by yours truly.
3. Prior to connecting the S2340T's USB3 cable to the new PC, the most recent version of DisplayLink was installed (according to the Dell's setup instructions for this Monitor), as well as the A00-00_0N9PX Driver, to provide the relevant infrastructure for:
      a. The Monitor's Touch functionality,
      b. The Monitor's docking options (Ethernet, USB,. Audio),
      c. For the Monitor's USB connectivity (if so chosen in Windows' Settings).
4. None of the above however had anything to do with my prior PC (on which, incidentally, under a similar setup, the said Error message would not appear).

As for the physical connection, the Monitor is connected to the nVidia Quadro 4000 card by DisplayPort, and -- as stated above -- to the PC's motherboard by an USB 3.x connector (on the previous PC, the place of the DP connector was filled-in by an HDMI one).

Hope this throws some further light on the matter.

Thanks again,

Eric

I guess I'm not understanding. Your system is showing 2 monitors:

9:02:42.778......Monitor name = Dell S2340T (DP)
19:02:42.787......Monitor handle = 0001008B
19:02:42.788......Monitor screen area = 0,0 x 1920,1080 1920x1080
19:02:42.789......Monitor work area = 0,0 x 1920,1050 1920x1050

19:02:43.583......Monitor name = Dell S2340T (HDMI)
19:02:43.588......Monitor handle = 00020001
19:02:43.588......Monitor screen area = 1920,0 x 3840,1080 1920x1080
19:02:43.589......Monitor work area = 1920,0 x 3840,1050 1920x1050

Do you have 2 different S2340Ts? If not, then one is a phantom, generated by the DisplayLink driver, and needs to be removed.

Dear Argentum,

Thanks for the continued support

No, I have a SINGLE monitor, connected however (as per its installation instructions) in two different manners: DP & USB (the USB connection serving also as the means for enabling all the other functions of this monitor (Ethernet, USB Hub, Audio, Camera). 

Page 20 of the UserGuide (see < https://downloads.dell.com/manuals/all-products/esuprt_display_projector/esuprt_display/dell-s2340t-multi-touch-monitor_user%27s%20guide_en-us.pdf >) explains that after connecting the DP/HDMI (one of them) cable, DisplayLink is to be installed and the USB cable connected too.

The above procedure however creates, indeed, a 2nd "phantom" display, which can be accessed by switching the input source via the physical selection buttons on the Monitor (at which time the DP/HDMI would become the "phantom" one).

Based on your insight, I rechecked Windows' Display Settings, and discovered that the two (physical & phantom) monitors were set as an extension one of the other (instead of the duplicate setting that was expected in this case).

Further to which, I changed the setting to "Duplicate", stopped DDM and started it anew, and ... the error message no longer appeared!

Guess this was the culprit, and -- if so -- thanks for helping discover it!

Just in case, I created one more diagnostic report, after the change and DDM's restart; would you kindly check it and see if there is anything relevant changed in it (which may explain the fixing of the error)?

Thanks again,

Eric

=========== Report beginning ==========

Diagnostic Report, generated 13-Nov-20 (10.0.19042)
Copyright (c) 1995-2020, EnTech Taiwan.
Version = 1.51.0.2015
OS = 10.0.19042.2 x64
Mechanism = 3
Account = Standard
Command line = "C:\Program Files (x86)\Dell\Dell Display Manager\ddm.exe"
////////////////////////////////////////
Configuration settings:
DriverError = Dell S2340T=NVidia
LastCheck = 0x0000AC6E
HintShown = 0x00000001
AutoRestoreWindowLayout = 0x00000000
GlassBorder.DEL4085.NWGM8332EESL = 0x00000100
AppScan.DEL4085.NWGM8332EESL = 0x00000004
DEL4085 = 0x00000001
FW.DEL4085.NWGM8332EESL = 0x00000003
EApolicy = 2000 2000 2000 2000 2000 2000
EnumErrorCount = 0x00000000
////////////////////////////////////////
22:34:02.069...Log opened
22:34:02.107...WinOS = 19042
22:34:02.273...LanguageID = 00000409 00000409 00000409
22:34:02.318...Build = 1.51.0.2015
22:34:02.322...Windows handles = 000201D8 00021074 000201D4
22:34:02.328...OS monitor sleep timeout value = 900 ms.
22:34:02.330...Applied DPI = 96-96
22:34:02.332...VM = 0
22:34:02.335...Registered DDM popup hotkey = Shift+Ctrl+D 6044
22:34:02.337...Registered EA layout MRU hotkey = Shift+Ctrl+Home 6024
22:34:02.339...Registered application window hotkey = Shift+Ctrl+Ins 602D
22:34:02.350...Remote asset management = 1
22:34:02.352...Remote registry service state = 4
22:34:02.914...WMI service state (unless firewalled) = 1
22:34:03.474...DMA = 3
22:34:03.486...Starting enumeration
22:34:03.628...1. DEL4084.8R33926O00QS on NVIDIA Quadro RTX 4000
22:34:03.634......Monitor assignment = 1
22:34:03.643......Adapter name = \\.\DISPLAY1
22:34:03.648......Monitor name = Dell S2340T (HDMI)
22:34:03.657......Vendor ID = 10DE
22:34:03.665......GPU driver = c:\windows\system32\driverstore\filerepository\nv_dispwi 27.21.14.5709
22:34:03.672......Flags = 00000005.00000003
22:34:03.677......Display tag = 8A028084
22:34:03.683......Monitor handle = 4DB71FBF
22:34:03.689......Duplicating monitor = MONITOR\DEL4085\{4d36e96e-e325-11ce-bfc1-08002be10318}\0003
22:34:03.695......Monitor screen area = 0,0 x 1920,1080 1920x1080
22:34:03.701......Monitor work area = 0,0 x 1920,1050 1920x1050
22:34:03.708......Monitor scaling factor = 100%
22:34:03.714......Raw EDID = 00FFFFFFFFFFFF0010AC8440535130301116010380331D78EA6430A35751A2270F5054A54B00714F8180A9C0D1C00101010101010101023A801871382D40582C4500FD1E1100001E000000FF00385233333932364F303051530A000000FC0044454C4C205332333430540A20000000FD00384C1E5111000A202020202020018A
22:34:03.970......Error: communicating via DDC/CI (0x0000001F) = A device attached to the system is not functioning
22:34:04.068......Error: failed to obtain output mask from display driver
22:34:06.820......Error: communicating via DDC/CI (0x0000001F) = A device attached to the system is not functioning
22:34:06.923......Error: failed to obtain output mask from display driver
22:34:12.153......Error: communicating via DDC/CI (0x0000001F) = A device attached to the system is not functioning
22:34:12.283......Error: failed to obtain output mask from display driver
22:34:12.290......Discarding unsupported display: DEL4084.8R33926O00QS on NVIDIA Quadro RTX 4000
22:34:12.365...1. DEL4085.NWGM8332EESL on NVIDIA Quadro RTX 4000
22:34:12.368......Monitor assignment = 1
22:34:12.370......Adapter name = \\.\DISPLAY1
22:34:12.375......Monitor name = Dell S2340T (DP)
22:34:12.378......Vendor ID = 10DE
22:34:12.383......GPU driver = c:\windows\system32\driverstore\filerepository\nv_dispwi 27.21.14.5709
22:34:12.385......Flags = 00000005.00000003
22:34:12.387......Display tag = A502A584
22:34:12.390......Monitor handle = 4DB71FBF
22:34:12.393......Duplicating monitor = MONITOR\DEL4084\{4d36e96e-e325-11ce-bfc1-08002be10318}\0004
22:34:12.396......Monitor screen area = 0,0 x 1920,1080 1920x1080
22:34:12.399......Monitor work area = 0,0 x 1920,1050 1920x1050
22:34:12.401......Monitor scaling factor = 100%
22:34:12.404......Raw EDID = 00FFFFFFFFFFFF0010AC85404C53454509170104A5331D783A6431A35751A2270F5054A54B00714F8180A9C0D1C00101010101010101023A801871382D40582C4500FD1E1100001E000000FF004E57474D383333324545534C0A000000FC0044454C4C205332333430540A20000000FD00384C1E5111010A20202020202001A5
22:34:12.468......VCP10 = 0064004B
22:34:12.472......OS device handle = 4DB71FBF.00000001
22:34:12.476......Capabilities string = (prot(monitor)type(lcd)model(s2340t)cmds(01 02 03 07 0c e3 f3)vcp(02 04 05 06 08 10 12 14(05 08 0b 0c) 16 18 1a 52 60(0f 11) ac ae b2 b6 c8 c9 d6(01 04 05) dc(00 02 03 05) df e0 e1 e2(00 01 02 04 06 0e 12 14) f0(00 01) f1 f2)mswhql(1)asset_eep(40)mccs_ver(2.1)) (cached)
22:34:12.784......Firmware string = M3T003
22:34:12.802......Configuration = FF0003.FF0074.1709
22:34:12.813......Model = Dell S2340T
22:34:12.820......Model year = FY13
22:34:12.824......Opcodes supported = 02,04,05,06,08,10,12,14,16,18,1A,52,60,AC,AE,B2,B6,C8,C9,D6,DC,DF,E0,E1,E2,F0,F1,F2
22:34:12.947......Timing = 67.50 kHz (+), 59.90 Hz (-)
22:34:12.957......Status = 0040009D
22:34:12.964...Ending enumeration
22:34:12.977...New=DEL4084.0004 DEL4085.0003
22:34:13.057...Creating VCP table on DEL4085.NWGM8332EESL
22:34:13.128......Opcode 0x12 = 0064004B
22:34:13.248......Opcode 0x60 = 000F000F
22:34:13.368......Opcode 0xE2 = 00160000
22:34:13.891...Video power down timeout = 900
22:34:13.902...User session connect
22:34:13.906...Display powered ON
22:34:14.018...Auto-saving window layout...
22:36:25.645...\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
22:36:25.648...Dump: Windows device enumeration
22:36:25.701...Display adapters:
22:36:25.712.....1.DELL S2340T USB
22:36:25.714.....2.DELL S2340T USB
22:36:25.716.....3.NVIDIA Quadro RTX 4000
22:36:25.720...Monitors:
22:36:25.732.....1.Dell S2340T (DP)
22:36:25.733.....2.Dell S2340T (HDMI)
22:36:25.735...Visible monitors = 1
22:36:25.737...1.DeviceName = \\.\DISPLAY1
22:36:25.739.....DeviceFlags = 00000005
22:36:25.740.....DeviceString = NVIDIA Quadro RTX 4000
22:36:25.741.....DeviceID = PCI\VEN_10DE&DEV_1EB1&SUBSYS_12A010DE&REV_A1
22:36:25.744.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{90862476-A8A7-11EA-BE78-EAC529B4A600}\0000
22:36:25.746.....a.MonitorName = \\.\DISPLAY1\Monitor0
22:36:25.748.......MonitorFlags = 00000003
22:36:25.750.......MonitorString = Dell S2340T (HDMI)
22:36:25.751.......MonitorID = MONITOR\DEL4084\{4d36e96e-e325-11ce-bfc1-08002be10318}\0004
22:36:25.753.......MonitorKey = \Registry\Machine\System\CurrentControlSet\Control\Class\{4d36e96e-e325-11ce-bfc1-08002be10318}\0004
22:36:25.757.......Raw EDID = 00FFFFFFFFFFFF0010AC8440535130301116010380331D78EA6430A35751A2270F5054A54B00714F8180A9C0D1C00101010101010101023A801871382D40582C4500FD1E1100001E000000FF00385233333932364F303051530A000000FC0044454C4C205332333430540A20000000FD00384C1E5111000A202020202020018A
22:36:25.765.....b.MonitorName = \\.\DISPLAY1\Monitor1
22:36:25.772.......MonitorFlags = 00000003
22:36:25.779.......MonitorString = Dell S2340T (DP)
22:36:25.784.......MonitorID = MONITOR\DEL4085\{4d36e96e-e325-11ce-bfc1-08002be10318}\0003
22:36:25.788.......MonitorKey = \Registry\Machine\System\CurrentControlSet\Control\Class\{4d36e96e-e325-11ce-bfc1-08002be10318}\0003
22:36:25.793.......Raw EDID = 00FFFFFFFFFFFF0010AC85404C53454509170104A5331D783A6431A35751A2270F5054A54B00714F8180A9C0D1C00101010101010101023A801871382D40582C4500FD1E1100001E000000FF004E57474D383333324545534C0A000000FC0044454C4C205332333430540A20000000FD00384C1E5111010A20202020202001A5
22:36:25.796...2.DeviceName = \\.\DISPLAY2
22:36:25.799.....DeviceFlags = 00000000
22:36:25.802.....DeviceString = NVIDIA Quadro RTX 4000
22:36:25.804.....DeviceID = PCI\VEN_10DE&DEV_1EB1&SUBSYS_12A010DE&REV_A1
22:36:25.807.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{90862476-A8A7-11EA-BE78-EAC529B4A600}\0001
22:36:25.811...3.DeviceName = \\.\DISPLAY3
22:36:25.814.....DeviceFlags = 00000000
22:36:25.817.....DeviceString = NVIDIA Quadro RTX 4000
22:36:25.819.....DeviceID = PCI\VEN_10DE&DEV_1EB1&SUBSYS_12A010DE&REV_A1
22:36:25.823.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{90862476-A8A7-11EA-BE78-EAC529B4A600}\0002
22:36:25.827...4.DeviceName = \\.\DISPLAY4
22:36:25.829.....DeviceFlags = 00000000
22:36:25.831.....DeviceString = NVIDIA Quadro RTX 4000
22:36:25.834.....DeviceID = PCI\VEN_10DE&DEV_1EB1&SUBSYS_12A010DE&REV_A1
22:36:25.836.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{90862476-A8A7-11EA-BE78-EAC529B4A600}\0003
22:36:25.841...5.DeviceName = \\.\DISPLAY5
22:36:25.843.....DeviceFlags = 00000000
22:36:25.845.....DeviceString = DisplayLink USB Device
22:36:25.848.....DeviceID = USB\VID_17E9&PID_4312&REV_3122&MI_00
22:36:25.851.....DeviceKey = \Registry\Machine\System\CurrentControlSet\Control\Video\{C30AA74A-2066-11EB-BEA6-380025257A00}\0000
22:36:25.854...Total number of monitors enumerated = 2
22:36:25.858...\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
22:36:25.860...Dumping VCP table on DEL4085.NWGM8332EESL
22:36:25.928......Opcode 0x02 = 00020001
22:36:26.048......Opcode 0x10 = 0064004B
22:36:26.169......Opcode 0x12 = 0064004B
22:36:26.290......Opcode 0x14 = 000C0005
22:36:26.410......Opcode 0x16 = 00640064
22:36:26.531......Opcode 0x18 = 00640064
22:36:26.651......Opcode 0x1A = 00640064
22:36:26.773......Opcode 0x52 = 00FF0000
22:36:26.907......Opcode 0x60 = 000F000F
22:36:27.027......Opcode 0xAC = 000107AC
22:36:27.147......Opcode 0xAE = FFFF1766
22:36:27.267......Opcode 0xB2 = 00010001
22:36:27.387......Opcode 0xB6 = 00050003
22:36:27.507......Opcode 0xC8 = 00247309
22:36:27.629......Opcode 0xC9 = FFFF0003
22:36:27.749......Opcode 0xD6 = 00050001
22:36:27.868......Opcode 0xDC = 00050000
22:36:27.988......Opcode 0xDF = FFFF0201
22:36:28.108......Opcode 0xE2 = 00160000
22:36:28.228......Opcode 0xF0 = 00FF0000
22:36:28.348......Opcode 0xF1 = 00FF0003
22:36:28.470......Opcode 0xF2 = 00FF0000
22:36:28.529......VCP table dumped

=========== Report end ==============

You have disabled the phantom rather than removing it, which is ok but not a permanent solution. At some point you may want to go into Device Manager, and delete the USB entries under "Display adapters" because you are using a direct link from the NVidia gfx card to the S2340T. The USB display adapters exists for the use of those who prefer a single USB3 cable solution instead of DP or HDMI, or who lack the video outputs provided by your NVidia card. Its not recommended that you use USB video when you have NVidia graphics.

Its possible that the latest DisplayLink software would fix this issue automatically; you can find it here and recommended by Dell here.

Incidentally, the error notification you saw from DDM is new to the latest b.2015; it was not in older versions so that may be why you see it on your new PC but not the old one.

Dear Argentum,

Thanks again for the reply & insight.

Indeed, if the specific error message is new to the current (2015) version of DDM, this would explain the lack of it on previous installs.

Using the USB connection however doesn’t appear to be optional, for it is through this upstream connection that all the functionality of the monitor’s stand (Ethernet, USB hub, audio) as well as the built-in camera and the touch control are enabled.

For all I understand from the installation instructions, for all of the above to function, DisplayLink drivers are to be installed, and they – in turn – also create\ enable the USB monitor display entry … (in other words, for as long as extended\ full functionality of the monitor is required, the 2nd display entry is to be created, for DisplayLink doesn’t offer an option for functionality selection …)

Incidentally: as I mentioned in a previous message, I did install the most recent version of the DisplayLink drivers \ software (as listed at DisplayLink’s Web site, to which you pointed me as well).

Having said that, I guess that removing the USB display from the Device Manager will NOT solve the problem, because the whole thing is PnP (meaning that Windows will rediscover the USB monitor and bring back\ recreate the Device Manager entry).

However, the switch from “extend” to “duplicate” in the Windows’ Display Settings was necessary not only for hiding \ disabling the phantom entry (which appears to have been a side-effect), but rather for actual usability of the USB monitor (not that I am using it in any way …): for as long as it was defined as “extend”, it would display a mostly empty Windows screen instead of the regular one with all the icons of the software installed on the PC …

Repeated thanks for your support,

Be wll & keep safe,

Eric