It might be clogged AND jammed. Try inserting a 1/4 inch allen wrench into the socket in the bottom center and turning back and forth to free the rotor. If that doesn't work, open up the rubber guard at the drain and shine a light into the disposer (power off!) to see if a dish rag or something may be visible. Be careful sticking your hand into the disposer: They're designed to break bones. Best to throw the breaker or unplug the machine first.