Power head on epic 6500 does not work, is there a belt?

This is a bot of a blind guess, I don't know the model. But most power head cleaners I have worked on use the suction of the vaccuum to spin a turbo fan in the head (like blowing a child's windmill). The head not spinning is usually because there's not enough **** to spin the turbo fan. Check for:
Gummed up brush bearings (dirt or damp) making the brush harder to turn than it should be.
Poor suction caused by a blocked or partially blocked pipe.
An obstruction that is tactchin the beater or the turbo fan.
Blocked filters on the cleaner, reducing the **** and thereby not providing enough vaccuum to spin the beater.