Lots of things could have happened...that's why I would suggest that you use a digital multi meter to test the two lines going into the amp. Sometimes fuses look good, but are actually blown.

You could even grab a simple 12volt instrument light, connect a pair of leads to that, and test these lines to make sure they go hot when they should.

That and the fuses are the first step in checking it out...it's going to take some detective work.