There are several reasons an amplifier may go into Protect Mode. Oftentimes, this is due to a problem with the circuitry, like a short circuit or a working overload. Additionally, if there is excessive heat build-up from being played at too high of a volume level or from blocked vents or overcrowding in the area surrounding the amp, it will trigger the amp to go into Protect Mode in order to prevent any permanent damage that could occur. So if you find your amp entering Protect Mode unexpectedly, take some time to look for potential issues and fix them accordingly before using your amp again.