You need to find out if the motor has any sort of sound while in a game. It should be obvious since it runs the entire game. He can try manually turning the glove motor shaft from under the play field and see if that helps. If no sound from the motor start with the glove relay under the playfield. Try manually switching it on see if anything happens.

If the motor sounds like it is on, check the set screw that connects the motor to the glove assembly. If the set screw checks out ok and the motor is running but kinda has a grinding noise you might have to get new bushings for the inside of the motor.

Good luck!