Something wrong with tape mechanism. The heads are not moving in the right position to turn the tapes: both answering and receiving. They are permanently in a middle position.
you will need to repalce the drive belt. I have done this on about 8 of these untis in the last few years - they're all going slack. open the bottom cover and rotate the capstan gently to release the head mech and remove the cassette. take the old belt to a local part supplier or try cpc or molgar online.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cassette players.