Z790 ProArt built in igpu not working on i9 -13900T

[Extravaganza]

I have a new Asus ProArt Z790-Creator WiFi motherboard, and i9-13900T cpu. 

If its all put together with a discrete graphic card it boots up fine.

If it take the discrete graphic card out the built in iGPU does not post. I have updated to latest Bios 1801, and reset the c-mos, and still nothing. All i get is 1 long 3 short beeps and white Q-LED is on. The error looks like no iGPU UHD 770 Graphics  VGA is supported (there is no signal in HDMI motherboard output). I need to get it working and that CPU should work as well. 

One more thing is when the discrete graphic card is in and i go to the bios you don't have an option for internal iGPU to select primary display. If anyone has a way to get it working?

Thanks in advance

[Jiaszzz_ASUS]

Hello, @Extravaganza 

We have internally verified that the ProArt z790 Creator WiFi with BIOS version 1801 and i9 13900T are able to correctly output graphics via iGPU.
Based on your description, we recommend contacting the place of purchase for after-sales assistance or reaching out to ASUS service center to arrange further diagnostic and repair services.

Thank you.

[Extravaganza]

Thank you for your response.

What settings have you set in BIOS to boot the computer correctly ?
I am not even able to get into BIOS (I can do it only with discrete graphic card connected to PCIe socket, I have borrowed from my colleague)
I was trying many different settings in BIOS (with UEFI set to on and off, and turning off on-board devices, removing one RAM module - nothing helped so far).
I have trying to start the computer with monitor connected to on-board HDMI port and without and it didn't help as well.

There is no tutorial on the Internet what settings to set in BIOS for the computer to start working .
I have nvidia H100 GPU but it has no HDMI port at all, so I need iGPU to be working (the nVidia GPU card is not connected to PCIe port during tests).

I have contacted Asus service center before. They said exactly the same you said - the configuration I've got is working on their side.

Thank you