Home theater. I have a Harmankarden receiver AVR 240 that now continues to give the "Protect"

Question

I have a Harmankarden receiver AVR 240 that now continues to give the "Protect" wording on the main panel and then shuts down. I've looked through the system manual and can't find the answer. Please help. The higher the volumn the sooner it flashes and turns the unit off even when only at half power.