Stereo problem with amp?

My prelude came with an 400 watt 2 channel amp and a rockford fosgate sub. It would not work when i got it so i took out the amp and sub. I tried to put it back in yesterday and it worked. So i tried to place the amp in the trunk and the grounding wire came loose so i tried to reconnect it but the trunk light went off and so did the stereo itself. Anyways when i was riding in the car the stereo would periodically come on but then shut off. What should i do now?