With the auger housing attached to the motor unit make sure it is fully locked in place. Try motor unit. you should be able to see the motor turning by looking down the front of the grinder. Shut off!!! Now put in the auger and make sure it is full inserted, try again. It should turn easily. Shut off, add the knife with the sharp side facing out. add the plate making sure the indexing hole/pin in in the correct position, now add the locking ring just on loosley. Try motor again, if turning tighten the locking ring.

Things that can go wrong:
auger not seated in motor unit
Knife in backwards
Plate not indexed in
knife on the wrong side of plate
motor NFG.