One or both of the tape reels might be stuck.
Try inserting a butter knife blade or something just a bit wider between the teeth of either of the reels, and then see if you can turn the reel.
It should take some effort to turn the reel, but not a lot.
If you don’t have something wide enough to simultaneously engage the teeth on the opposing sides of the reel, you can angle the blade of a butter knife so that it bridges the gap.
If you can’t turn the reel in either direction, then try the same thing with the other reel.
If you can’t turn either reel in either direction, then you have at least one frozen reel, which would cause the trouble.