Erp! It's stopped working!

It worked fine for a couple of days and now no sound again

I've had the dash apart and have recrimped the connection - it's definitely good. So what else could be causing a lack of sound? I've no idea if the amp is powering on or not - there doesn't seem to be a way to check, but I'm guessing it's not.

I tried to check for some sort of voltage on the blue wire when turning the headunit on, and there didn't seem to be anything coming from it at all.