Protection light is on

Check power make sure you have solid 12 volts. Disconnect speakers, shorted speaker can cause protection mode to engage. If still in protect mode will need to repair. Kicker does out of warranty repairs on kx series amps or try T.I.P.S contact at linearpower.com. Iirc Ray @ tips was one of the engineers at kicker back when kx series was introduced.

Replace amp

To many speakers not enough amp

Disconnect all the wires except the three main power wires, ground, 12v battery and remote. Now, turn on your radio, if the protect light is still on then there's an internal short in the amp. If the light turns green, then there's a short in either the auxiliary cables or the speaker outs. If it turns green, then troubleshoot the other wires that plug into the amp by connecting them one at a time until the protect light comes on, which will tell you that there's a problem with that speaker/aux wire.

try hooking up only the power ground and remote see what happens if protection light is on then u have a problem with amp if it goes off then hook up rca if still off then hook up speaker wire if it turns on then u have a prob with speakers

that would be the amp. sorry to say. when a wire crosses over, it sends a shock through the amp, there are a few things to try just to see if you fried the amp. the first thing to try is to move your ground to a different location. second thing to look at would be the fuses. alot of times the fuses will blow at the slightest shock. the amp will still turn on if you have an amp with 2 fuses, it just wont be getting all the power it needs, which could be causing your problem. also, it is worth the hour and a half to mount everything down in your vehicle. you might check the kicker website, because i have herd rumors that kicker offers a lifetime warranty on almost all of their products. best of luck, and i hope you didnt fry your amp.

if the amp is powering on the sub and playing and then turns in to protect mode it could be the amp is getting hot and its kicking into protect so you wont fry the amp

Could be the power supply or output stage electrolytic capacitors.
Possibly breaking down/drying out inside.

There is a short some were check all hot wirs for any bare spots . If that is not it most likley when you installed it you blue italways hook main hot wire last.

Generally, when an amplifier goes into protection when you attempt to power it up, it means that the output transistors have failed.

Measure the DC voltage across the B+ and ground terminals as well as across remote and ground. If you have less than 11 volts when the amp tries to power up, the amp could be shutting down due to low voltage.

If the voltage remains near or above 12v, disconnect all speaker wires and signal cables from the amp. If it powers up, the wiring needs to be checked. If it still shuts down, the amp likely has blown output transistors.