old style hopper with the motor off to the side?
if so, you should be able to push on the nubs sticking out of the pinwheel and move the disc in both directions a little due to the lash/slop in the gears. if you can't budge the pinwheel, time to take the thing apart. The shaft could be cruddy or the dirt that accumulates at the bottom/behind can bind things up.
you won't be able to move the pinwheel once the gear lash is gone due to the gearbox torque.
the shaft sticking out the end of the motor armature/rotor shouldn't spin freely ... spinning that should slowly turn the pinwheel. If the pinwheel did bind up, the motor may have lost some gear teeth.
the hopper motor is 120V, so you can attach a power cord to the motor winding lugs and plug it into the wall to see what happens. If that works, check the payout relay contacts for burning/pitting/adjustment. The payout relay switch wires are usually white and white/blue and there's two switches in parallel. The white/blue goes to the hopper motor winding.