First things first, read your manual and observe all warnings on the amplifier in regards to the dangers lurking inside BEFORE you decide to open the amp. Opening/working on your amplifier can be potentially very dangerous, especially if you do not know what you are doing. It goes without saying that if you have very little knowledge of consumer electronics or things that go zapp in general, take it to a qualified and trustworthy technician. That being said...
It sounds like a blown fuse, which also could be an indication of something more serious happening, but hopefully not. You are going to want to replace the fuse and try the amp in a receptacle (outlet) that you know is operating 100% properly. (proper voltage/no wiring issues as in older homes.) If the fuse blows again right away, something more serious is up.
Consult your manual or the proper schematic to make sure you replace it with the correct fuse. DO NOT only go on the one that was in there, unless you bought it new and are absolutely certain that it is the original fuse. Either way it doesn't hurt to consult the manual or schem. If it is a thread-type fuse (it looks like a glass tube with a filament running through the middle) you might be able to tell that is blown upon visual inspection. If it is blown, little pieces of the thread will be scattered throughout the tube. To be positive it is blown, you can check its continuity with a multi-meter, if you have one. Or you can just replace the fuse anyway....they are usually very cheap.
ALSO: it could be that the "on" switch went bad. I just worked on an amp that would not turn on because the rocker switch went bad (and a fuse blew) and needed to be replaced - which is amazing considering they are usually rated at 10,000 uses before failure or something like that
Good luck and I hope you fix your amp. One of mine was just busted too and I know how much it sucks.