My Kicker 04KX400.1 stopped working. Che...

Hello dbarlow_it,

You do not say if the amp is showing an indication of powering up or not. If it is getting power, the "power" LED should be lit.

There's also an inline main power fuse that should be located within a foot or two of the positive battery terminal. If you have checked it also and it's good, test for 12V+ at the amp power terminal. If you are getting power, then check that the remote turn-on lead is still functioning. It should also have 12V+ on it when the receiver/head unit is turned on.
If the amp is getting power, and a turn-on signal from the remote, it's most likely that the amp itself is defective.

Hope this helps.