This has happened to me, except with actual compressed air. I turned off, unplugged, and discharged the PC, just because I always do that before opening it up. I then popped off the panel and used my trusty compressed air can to dust it out. Put everything back in place, and nothing.

I’ve worked in tech long enough that I was actually shocked when the problem didn’t turn out to be something stupid I missed, like flipping the supply’s power switch. The damned PSU somehow killed itself on a previously-unused can of compressed air.