Disposer only making a humming sound when you run it or it will not run at all. Check the breaker under the disposer, reset the breaker by pushing it back in. Look at picture, the red button is the breaker. Try the disposer if it still humms stop and do not attempt to run it, something is jamming it . The first thing you should do is unplug the unit from the power source.
Using a flashlight shine down into the disposer cavity and see if there is any debrie along the edges that might be causing it to jam. Usually something like a coin can get jammed a long the side of the unit not allowing to spin .Use a screwdriver or similar tool to free the object. Once you have loosened the debrie or the object, Use gloves or get a little dirty, take you're hand and pull the object out of the disposer. You can also use a long pair of needlenose pliers to remove the object.
Try to free the disposer by using an allen wrench and placing the it in the center of the disposer shaft and turn as hard as you can to the left or right so you can free up the the debrie or the object hopefully this will unjammed the disposer.