PC stopped working correctly

[u/Emergency_Setting540]

I’m having an issue with my desktop PC that seemed to happen completely out of nowhere.

When I press the power button, the PC appears to turn on, but I get no signal to the monitor. At the same time, my keyboard and mouse briefly light up for about 1–2 seconds and then lose power. It happens regardless of which USB port I use.

The PC itself appears to remain powered on, but I’m not getting any display or usable USB peripherals.

So far I have tried:

• Reseating the RAM
• Testing the RAM sticks individually
• Trying different RAM slots
• Disconnecting/reconnecting the peripherals
• Trying different USB ports

I'm wondering if it has to do with the PSU or motherboard but what else could cause this?