Question No video signal after turning PC off during Windows 11 setup process ?

[MagBoi]

I built my brother (who I do not live with, so I can't directly look at or try to fix it), a PC during the day and it posted into bios perfectly with no issues. I forgot to bring a drive with a Windows installer, so he had to do it alone. He then later texted me, saying he couldn't get it to connect to wifi during the Windows Setup process, so he tried turning the system off. But then when he tried to turn it on again, there was no video, but the system lit up. He tried waiting 10 minutes for a signal, used an HDMI and DisplayPort cable that was plugged into the GPU, the monitor works with other devices, tried reseating ram and cmos battery but still nothing.

I would greatly appreciate any troubleshooting tips, or any insight as to what may have caused it. Again I'm only relying on the information he gave me, as I can't directly interact with the PC.
These are the parts used: https://pcpartpicker.com/list/MnRcXy

Update: He tried installing an old gpu and it posted, but he couldn't get his mouse and keyboard to register in the bios, so he tried turning it off again, but now that gpu wont post. He also said that the system turned off almost immediately after pressing the power button.

 

[Lutfij]

Might want to suggest that he clear the CMOS. Disconnect from the wall and display, remove the CMOS battery, press and hold down the power button for 30 seconds to drain any residual power, then replace the battery after 30 mins. You might want to parse this URL to help with offline Windows 11 OS install.

If the BIOS is what went corrupt;
https://dlcdnets.asus.com/pub/ASUS/...-A_WIFI_UM_V3_WEB.pdf?model=PRIME Z790-A WIFI
turn to page 3-4 in your motherboard's manual, section 3.4, ASUS CrashFree BIOS 3. See if that helps him revive the platform if the clear CMOS doesn't work.