push the sub down see if it will move down if not the sub is blown check the rca cables that delivers the nots to play turn the filter on amp to lowpass
check you ground sometimes an amp will turn on like everythings fine like it recieves some ground from the rca but will not play if it has a bad ground also try the sub elseware or a different speaker on the amp to distinguish which one has a problem also your deck might have an on/off if your using a sub output from your head unit
check you ground sometimes an amp will turn on like everythings fine like it recieves some ground from the rca but will not play if it has a bad ground also try the sub elseware or a different speaker on the amp to distinguish which one has a problem also your deck might have an on/off if your using a sub output from your head unit