|Have you tried it plugged into a different circuit in the house/building. The breaker may have been tripped or fried.|
If you are using a surge protector (or UPS), a lightning strike may have blown through the protection and either tripped its breaker or burnt out the last-chance non-replaceable fuse. Briefly, try directly in an outlet that you know works.
Try bypassing the case' power button and briefly short the 2 pins together with a metal screwdriver to see if it powers up.
Report results and anything else you see or hear that might help.
You have to be a little bit crazy to keep you from going insane.