There are a few possibilities. The mover deck blades are operated by a belt. Check that the belt isn't broken or slipped off the pulleys. To engage the blades, tension on the belt is tightened. Depending on your model, this is either done manually by shifting a lever, or electrically with a switch. Either way, there is a linkage which tightens the belt to engage the blades. Make sure this is functioning. There are generally several links that have to be disconnected when the deck is removed. They are held in place with pins. Maybe one of them has come out. If you have an electrical engage for the PTO, check the connections. There's no rocket science here, just a few things that should be obvious when you check them.