It will show the play icon and everything else--I can even hear the tape moving in the cassette, but it no longer plays.

Is this something I can fix or is this just impossible?

My main concern is just using it as an audio-in (with a cassette tape adapter for a DAP).

 

send one of those tape deck head cleaners through it. If you haven't used it in awhile, all the static electricity in the magnets for the heads would have attracted a bunch of dust