Activating an Add On Video Card

discrete video card does not need activation.

go inside dev manager (under settings>system) and look under display adapter tab.  does it list more than 1 video adapter.  if it only lists the intel HD graphics, then your pc does not detect the amd card.  you can try uninstall the card then reinstall it using proper technique.  if still not detected by pc, it may be a bad card for which you can ask Dell to ship you a replacement (and Dell will ask you to ship back the original card).

Unless you have VisionTek variant, Dell Radeon RX 550 does not have HDMI connector, only Displayport and mini-Displayport

Card is properly seated and its fans come on.

Correct, my mistake, it is displayport.  Both devices shown active with no errors in device manager.  Tried plugging into the card again, no deal, the monitor only works when plugged into the mainboard's displayport, the lower of the two.  Shouldn't this have been checked our prior to shipping?

Assuming you already verified BIOS settings for video display =  Auto.  Windows shows the device is working properly, visual check shows its fan is working.  The next possibility issue is with the output port.  Making sure that the cable connector is fully plugged into the displayport of the RX 550. 

You can also perform a hot swap cable test.  With the machine is running, removing cable from integrated graphics port and plugging into the RX 550 's displayport.  You must hear Windows sounds notifying device plug-in.  Sometimes, give it a minute or two for refresh rate adjustment and for video to display.

If no change, shut down and unplug the PC, discharge of residuary power, move the RX 550 to a different slot ( the x16 slot wired as x4).  Retest for signals.

Got into BIOS and Display Adapter was on AUTO.  The AMD card was listed, so I selected that, connected the cable to the card and rebooted.  Still nothing.  Now another problem.  Moved the cable back to the motherboard port, there is no recognition of the monitor during bootup for about 2 minutes so F2 to get to the menu doesn't work so I can't get back into the BIOS to change back to AUTO to at least use the onboard graphics.  I guess I'm going to have to reset the BIOS to defaults to clear it so it recognizes the onboard graphics again. 

Also, swapped out the card with another and same results as above, so it is the slot or motherboard causing this.  Have not actually inserted that card in another computer, though, but same results with another card.  By the way, the lack of recognition of the card was happening right out of the box under Windows 10.  Have since upgraded to Windows 11 with same results.

Your machine just went through a refurbished process (recently worked on), only a slim chance of faulty video card out of the box.  I would focus on other factors such as proper cable, connection, monitor, drivers, display settings.

You can temporary remove the RX 550 from the machine, video display will revert back to the Intel integrated graphics.  In some similar cases, users reported that by leaving the machine on and connecting to the internet for several minutes, the display will appeared.  The reason was that while you were unable to see, as a new machine, Windows needed to run several updates, including proper display driver and when proper adjustments were done, the screen finally displayed. 

I suggest that connecting to integrated graphics so you can see and running Windows updates and installing all optional updates as well.  See if Windows will install Radeon display driver, then switch to the RX 550 to test again.

Installed drivers from AMD site and same deal.  I am suspecting the connection, the monitor side is HDMI and the card side is displayport, I have ordered displayport to displayport cable, hopefully that resolves it.

It is always good idea to use straight DP to DP or hdmi to hdmi cable than an adapter, but in your case the adapter cable works for integrated video.

Re: the lack of recognition of the card was happening right out of the box under Windows 10

Is it possible that the current bios settings is such that it sends video to integrated as primary video, and discrete card as secondary video in a multi display fashion?  Since you have only one monitor, when you unplug video cable from igpu and move to dGPU, or back, it caused some untoward confusion in bios.  If you have another monitor with DP port, try a dual monitor test: one to integrated video, the second monitor to discrete card.  I suspect it might be a bios bug but not a motherboard hardware defect as the card is detected.  User reported Dell factory sometimes neglected to fix video port issue for brand new recent model Optiplex (7080/7090 iirc) oob.

Went into BIOS and multidisplay was checked.  I had been leaving it like that, because it said that it should be enabled on Windows 7 and later.  On bootup, message came up saying that an external video card was present and to plug the video cable into that (was presently plugged into internal graphics).  So I did that and now neither video is working, so back to clearing BIOS.  Still waiting on the cable to see if that will help.

Re: Both devices shown active with no errors in device manager.  Tried plugging into the card again, no deal, the monitor only works when plugged into the mainboard's displayport, the lower of the two. …I did that and now neither video is working

it is certainly an intriguing, but I am a bit uncertain of the multiple scenario here.  

scenario #1: connect video cable to onboard, start pc, enter bios>video option, switch from AUTO to AMD, which subsequently loses onboard video for 2 minutes.  need to clear cmos settings to return to baseline.

scenario #2: connect video cable to onboard, start pc, get error message video, hot swap cable to card, no video, hot swap back to onboard video, no video.
what did you do before you get this error message video?  Did you de-select Multi-display?

If both correct, it seems the only way to get onboard video is bios>video>AUTO + multi-display.

Please upload a screenshot of bios>video right after bios reset.

Please confirm: