does it have a remote turn on cable that u hook directly to the head unit... i had this problem and i hooked the remote wire to the wrong wire on the head unit.... or maybe its a grounding problem... make sure its touching as much metal as possible. I tried to ground my amp and there is a glossy coating on the floor of my car under the carpet, i had to scrap this away to get a good connection
Try jumping the + terminal of the amp to the remote terminal. If it turns on then u used the wrong remote wire on your deck. If it doesn't turn on then you may not have power to the amp or worse(a bad amp).