Question Aorus Master x570 - really weird issue please help

[talshabi8]

Hi, I built my first PC with this parts:
Palit RTX 3080 GamingPro OC
AMD 3900x
Aorus Master x570
Seasonic FOCUS GX-850, 850W 80+ Gold

At first - The GPU was connected to PCI-E x16 I turned on the computer and everything seemed to be fine - lights, fans, rgb. I connected a monitor to the GPU HDMI and boom the computer went down and not turning in.
The computer do nothing when I try to turn it on - no fans no lights nothing (tried different cables, tried different PCI-E slot) unless I remove the GPU - than the computer is turning on.

Than I did 2 things:

1. Removed the battery for 1 minute
2. Updated the bios using the q flash+

Connected the GPU to PCI-E x8 and the computer is working again YAY! - this time no crashing when I connect the HDMI but no signal on the monitor (tried both HDMI and DP).
I changed the GPU back to PCI-E x16 turned on (while connected to the HDMI) and again the computer is not turning on, and now even when the GPU is in PCI-E x8. Again,only thing that helps is removing the GPU,
I tried to remove the battery again for 1 minute with no help.

I have really no clue where to start, at first I thought it's a faulty GPU but bios update and battery remove returned it back to live, so now I suspect the MB is faulty but it's really weird.

Should I update the bios again? Is it something with PCI-E x16?
Any idea what should be the problem here?

Thanks

 

[talshabi8]

Tested it with a different GPU and it works fine, so it's 100% faulty GPU