start testing the wiring behind the radio, and test the remote wire @ the amp for voltage.

Look up the wiring colors for your radio and test the +12V wire, the accessory wire, remote turn on wire etc...gotta find something out of the ordinary and then trace it from there.

I'm pretty positive it is a fuse, and it is not necessarily and "audio" fuse. The lights on the radio and the power itself are not all on the same fuse. I've had things in a system not work because random fuses like the domelight, and wiper fuses were blown. TEST EVERYTHING. Something is blown.