Most likely the belt has rotted away.
If the mechanism doesn't move, it burps out the tape.
It's not that hard to take apart and replace the belt.
You can take the bottom cover off. The cassette deck can
then be removed. Then you take the bottom cover off the deck.
If your belt is broke, you may have trouble routing it right.
Otherwise, note how the belt winds through the pulleys.
You may still be able to match up a belt from MCMinone.com
an electronic supply house.
I bought some years ago, IDK if they still have them.