Audio Help

Just refitted my subs and amp back into my car in a new box.

The amp is all working fine as far as i know. the green power light stays on and doesnt go to red to say there is an error. The amp is a monoblock

The sound through the subs come out fine sometimes, other times it doesnt come out at all, or makes sharp noises or is sometimes really quiet. The Subs are DB Raptors They are dual coils subs.

Anyone got any ideas on what the problem may be??

Many thanks