|Unplug the cable from the back of the power supply and leave it unplugged for 30 seconds. Also while off, if the power supply has an on/off switch, switch it off. Also, some power supplies have a green or amber light to confirm they have power, does yours? |
Plug it back in, switch it back on and see if you can get it to power on. If it doesn't come back on, I would suggest testing it with a power supply tester (or take it to a shop) and start narrowing down which equipment is good. (PSU, Motherboard, etc).