If you have an electric PTO, then the belt from the PTO to the deck should be tight at all times. Check to see that the idler pulley, making sure that it has full travel and moving freely. Also try this, turn the key switch to the run position, and turn the PTO switch on. You should hear the clutch engage. Also, you might have some one watch the clutch while you turn the PTO on, to see if it is engaging.