Sorry to hear about your problem. More information would be helpful.
1- Have you tried to manually advance the pucks?
2- Do you hear the motor running, when it is trying to advance the pucks?
a- If the moto is running, make sure the guide rails are free of any debris that may be blocking the shuttle from fully advancing. If there is any blockage the shuttle will only travel halfway, then the motor will reverse.
b- A loose linkage arm could also cause problems, make sure the linkage from the motor to the arm is alright.
c- If you can't hear the motor running, check for loose wiring; or your motor could be dead.
3- The generator doesn't have a belt. The motor is driven by plastic gears. These gears can strip, and if that is the case you will need to replace the motor.