I’m not totally familiar with that particular model…..but it sounds like the grinder is jammed. On many units, there is a small hole on the bottom near the center which accepts an Allen wrench and is used to crank the grinder back and forth in order to free up the jam forcefully.
Look on the bottom. If there’s a hole there, try seeing if an Allen wrench will fit into it and crank it (you may have to try several sizes). If this hole is not there, as is the case with some of the older, less expensive models, then your only choice is to get a long shank screwdriver or some other kind of tool and see if you can get the grinder to crank around from the top by pressing the tip of the driver against the inside of the disposal from top and banging it to free up the jam and make the grinder turn again.