@noelle Dunno if you've fixed this but I've had something similar and had to hold the power button as I pulled the power cord out of the back... then reinserted, and presto.
Dunno why but that's how I had to clear my tower a few times..
@noelle (And please feel free to tell me to go to hell for trying to give advice without being asked for it. lol)
@noelle Otherwise what you've described to IO sounds like a dead CPU (or a CPU not drawing power.)