My built PC just arbitrarily won’t turn on.

It was working as of 17:01 today. That’s when I powered it off using the button on the top. I came back at 22:00 and it refuses to turn on at all. No lights no nothing. It was plugged into a power surge protector. I have tested the wire using my voltmeter and it’s getting ~125VAC through the wire. I’m trying not to panic because my life is on that computer.