Check you connection at the battery and check that your ground wire has a clean and secure connection. I know that you said all fuses are fine, most amps have an inline fuse, did you check that also?
Today while I was driving, my aftermarket stereo shut off and wouldn't turn on... I'll plug the harness in and it will make it's normal sound but it doesn't durn on. Wiring is correct and no fuses are blown. My amp also isn't receiving any power either. What might be the issue? Battery issue? Or alternator?