Grounding 2 amps??

I have two 400 watt 4-channel amps pushing two 10" MMATS subs. I wired them up and I can only get one of the amps to ground. One of them works but they both have a good ground. I'm really stumped if anyone could help me out. If you need any more information just ask. Thanks

take a volt meter and make sure both amps are getting power from the power wire and remote turn on wire, it may not be the ground.
also try grounding the amp thats not working to the grounding post of the one amp that is to see if that is actually the problem