If the amplifier activates the protection circuit, this can have several causes.

1. the loudspeaker has a defect.
- Crossover/driver overloaded
- Connector has loosened and causes a short circuit.
2. the cables to the loudspeaker have a short circuit due to moving or cleaning the loudspeaker.
3. the amplifier has a defect.

If the amplifier goes into protection circuit, it should be disconnected from power directly.
Then you can remove the speaker wires and turn on the amplifier.
If the amplifier does not go into the protection circuit, it is probably due to point 1. or 2.
If the amplifier still goes into the protection circuit, the amplifier is probably defective.