Be sure that your PXE is enabled so that it will show on your one-time boot menu.  That's the only setting I can see that you didn't address specifically.

It's in the "Connections" link (left hand side) under "Integrated NIC Configuration".

On the old legacy BIOS interface, when you initiated a PXE boot, it would make you hit F12 again to confirm after the handoff.  On the 7080, you could hit F12 or Enter.  

Try hitting F12 or Enter so that your PXE request doesn't time itself out.  Does it give you any PXE errors when you try to do this?  Or just hang and then restart?

I also have same issue. PXE is enabled. It just hangs at the IPv4 screen and then eventually goes into troubleshooting mode.

Are you guys just letting it sit there or are you trying to hit Enter/F12 as prompted before it hangs?  

I know on the -80 and up series, the PXE interface is a bit different.  Old method is waiting for the screen prompt, hit F12 after the IP assignment, and continue via PXE into MDT (or whatever you're booting into).  New Method is waiting for the screen prompt, hit Enter, and continue via PXE into MDT (or whatever you're booting into).

Either way, it requires user input else it will hang and force you to reboot the machine...

The process is:

* Enable network boot and UEFI network stack in BIOS

* Boot system and tap F12

* Select the ipv4 pxe boot option

On the older systems, this then displays messages about starting PXE, media check passing, MAC address, IPV4 address, and the boot process starts properly.

On the newer systems, it hangs at "Starting PXE".

My DHCP server logs show that multiple requests are sent out by the system; the DHCP server offers a lease but evidently it's not accepted. The system then restarts into troubleshooting mode.

It's getting to be a bit of a problem because it means I can't image any new system without taking it apart...

Older system (7070-), after you hit F12 and it started PXE, it prompts you to hit F12 again or it stalls and forces reboot. 

Newer system (7080+), after you hit F12 and it started PXE, it prompts you to hit ENTER (But F12 also works) or it stalls and forces a reboot.

You are getting no PXE errors when trying to handoff and it doesn't tell you to hit any key to restart system?

Im still confused as to where you're stalling...

On older systems:

* Hit F12 on boot to enter boot menu

* Select PXE boot option (ipv4)

* PXE message appears on screen : shows 'Starting PXE', shows MAC address, shows IPv4 address

* PXE bootloader runs (Windows setup)

On newer systems:

* Hit F12 on boot to enter boot menu

* Select PXE boot option (ipv4)

* PXE message appears on screen: shows 'Starting PXE'

* Stays like this for about a minute before falling back into a 'boot failure' state.

* The DHCP server logs show that the system requests an IP address, is offered one, requests again, is offered again, requests again, is offered again - about 7 or 8 times.

So as far as I can tell, it looks like the PXE bootloader is not correctly interpreting the DHCP offer; and as such it is not accepting an IP address, and so doesn't work.

It's very strange that this loop wouldn't report a PXE error if that's the case.

After trying multiple things, I switched the HD in the BIOS from RAID to ACHI and was able to PXE boot and image the 7090's. 

 @wildfire7 , I have a 7090 optiplex, and I can't upload PXE images for it either. I've made several changes to the BIOS, including RAID to ACHI, but so far, nothing! Which NVMe / SSD driver are you using on your MDT? Here you can even find the PXE, but when you go to the list of Images, this error appears here:

  

Hi Verynoob. Have you tried downloading the newest WINPE drivers and updating your boot image?