A humming disposal that won’t spin almost always means the flywheel is jammed, usually by a piece of hard food, a utensil, or fibrous material caught between the grind ring and the impellers. The motor is still receiving power and trying to turn, which is the hum, but something mechanical is physically stopping it. Most units have a reset button on the bottom and a hex-key opening for manually freeing a jam, and that combination clears the majority of cases we see.
If the unit doesn’t hum at all, that usually points somewhere else entirely: a tripped breaker, a bad switch, or wiring, rather than the disposal’s mechanism itself, which changes the fix. We check both the electrical side and the mechanism before quoting anything, since replacing a disposal that only needed a reset button pressed is money spent for nothing.