Disconnect all wires from the amplifier except for the power wire and the ground wire. This means also disconnecting the remote lead, the RCA cables, and all the speaker wires.

Then use a small wire to touch the remote turn-on connection point to the power wire.

Does the amp power on now?

If so, the one of the connected things was shorting it out and preventing it from turning on. Reconnect them one at a time until you find which one it was.

If not, then the amp is bad or there is something wrong in the power wiring.