When a garbage disposal has a clog, an internal breaker may trip to prevent the motor from burning out. After clearing the clog, you'll have to reset the disposal to get it working again. Every disposal has a prominently placed red reset button for this purpose, although you'll have to crawl into a sink cabinet to find it. After you press it, the disposal should work, assuming you've actually cleared the clog, and the outlet into which you plugged the disposal or the breaker controlling the circuit hasn't also tripped.
The internal breaker in the garbage disposal trips when debris is stuck between the rotor and the sides of the canister, and if you reset the disposal before clearing this debris, the breaker will just trip again. To clear the clog, start by turning off the garbage disposal switch, then turn the rotor back and forth using the key that came with your disposal or a 1/4 -inch hex wrench. If your disposal doesn't have a slot for a hex wrench, you may need to use a conventional wrench. If there's nothing for the wrench to grab, insert a wooden spoon or broom handle through the mouth of the garbage disposal and use that to turn the rotor. No matter which method you use, the goal is to get the rotor spinning freely in both directions.
Using the Reset Button
After clearing the clog, you'll want to double check the switch to make sure it's off before resetting the disposal. Use a flashlight to locate the reset button. If you have an Insinkerator model, it's on the bottom of the canister. If you have another type, look for the button on the side of the canister, often near the point where the power cable attaches.
Press the button firmly until you hear it click. If it stays in, the disposal is reset. Turn on the water, then turn on the switch to start the disposal, which should now run normally.
The Disposal Won't Reset
You may find that the reset button doesn't stay in when you press it. That's usually because the GFI outlet into which you plugged the appliance also tripped. Locate it and press the reset button, which is the lower one. If the buttons have colors, it's the red one. If the outlet won't reset, check the breaker for the circuit in the main panel, because it may have tripped. Reset it by toggling it all the way to the off position and then turning it on.
If the breaker hasn't tripped, but the GFI won't reset, it's because another GFI outlet on the same circuit has tripped. This outlet could be outside or in the basement. It may take some detective work to find it.
You may find that the outlet has power, but the reset button on the disposal won't stay in. This is usually the sign of a defective motor. Call a service pro to diagnose the problem.