Have you checked the amp fuse ? also never connect while battery is connected. be sure to connect the amp to amp specs as stated in user manual i had the same problem and it was as simple as a missed connection however it could be a multitude of isues causeing the problem most of which are in the user manual. also check the earthing cable is hooked up and be sure no power supply is earthing out on the car. Protection mode is generaly activated when the amp isnt connected properly or by fault of power supply. double check evenrything and check again.

Disconnect all speaker connections and rca cables. Leave power, ground and remote wires intact. Try turning on again. If you still have a protection light your amp is faulty. Hopefully you have warranty. Double check all connections. GOOD LUCK.A thumbs up would be greatly appreciated if this answer is helpful to you. Worth fixing.

Check ur pwr. Cable fuse, if thats fine have a local repair technician take a look at your amp.