To avoid serious injury follow all warnings and instructions in the manual. Wear appropriate personal protective equipment.
Check wiring to the motor to ensure no bare wires are touching and that no wires are shorted to ground.
Unplug the directional valve (so pressure will not build up) and try to move the motor again. If this succeeds, then the power pack may need to be replaced. If the motor is still unable to move, the bearings or hydraulic pump have likely failed in the motor and will need to be replaced.