does the amp turn on? if not, make sure your ground is clean, and your power wire is not loose or anything....if your amp is on, then check your rca's and make sure you have your speaker wires on correct. I once tried to hook up my speaker wire a different way to my DVC subs and they didnt work, so i put the wires back to normal and everything came back on.

edit: since your using multiple amps and if you have a distro. block, make sure the fuse to your sub amp isn't blown (if your amp isn't turning on this could be another solution)