T5820 - BIOS codes state PC is fine but no Display

Hi

I have a T5820 Core-X i9 and a RTX 2080.  I couldn't get into the bios with F12, instead this brought a bios screen for networking or something I didn't understand. So I pulled out the CMOS battery, waited a minute and installed the battery and connected the power lead.  The PC started automatically but there is no display.  The power button LED is solid white.  the IT department in my work tested it and everything is fine.  The gpu works in another PC.  They managed to put the PC in bios recovery mode (led was 2 amber, 2 white) but no display.  They tried it with a 1080p monitor via HDMI and DP but still no display.  GPU was tested in both pci slots, no display.  They tried it with minimum RAM, no display.

Everything done so far points to the hardware being sound.  Does anyone know what else can be done?  Or is it possible for the Bios to be corrupt but not be reported correctly in the POST?

When plugging the power lead in after resetting the CMOS, it starts up automatically and sometimes restarts but eventually stays on with a solid white LED on the power button.  Is there a pattern to look out for and how long should it normally take for the BIOS/PC to boot into windows?

Thanks