Question PC won't POST after windows update

[Harkib]

After a windows 10 update, my PC never POSTed again. I'm not sure the update is at fault, however I have not made psychical changes.

When I press the power button nothing at all happens, no fans, no lights, no noises.

• I checked the power supply using the paperclip method (https://www.howtogeek.com/172933/how-can-i-test-my-computers-power-supply/) and it seems fine. The CPU cooler fans and LEDs turn and stay on.
• Removing 1 or both GPUs has no effect.
• Resetting the CMOS has no effect

The mother board has a CMOS reset button and power button that light up. Initially they will be on. After pressing the power button they will instantly go off. Resetting the power supply doesn't cause them to turn back on. Letting the system sit does not cause them to turn back on. Only having the power supply off for a while (15+ minutes) and turning it on causes them to turn on again.

The system;

• Aurus master x570
• Ryzen 3900x
• H150i Pro
• 2x 2070 Super
• HX850 PSU

My only hypothesis is a dead mother board. Is there anything else I should try before trying to get a replacement? Are there any other failures that could cause this behavior?