Please check for the belts if the battery you have installed is new and the set gives a hum on play. If not you will have to check the power switch, the mechanism switch and the line to the main board.
If the motor turns but not the capstan and the reel then change the belt, the rollers or the pulley. I hope this will get your set back to action. Good day
motor belts are cheap. try replacing the belt that drives the wheel. this become distorted specially when the unit has not been use for quit long time. if you think its not about belt, clean up the rubber that touches the tape when played, also the tape head with 70% alcohol. hope this help.