Nakamichi Dragon HELP - INOP

I have a Nak Dragon that came from someone quite famous - as I have spent some time upgrading (despite removing this great piece) many of his components - however, it is inoperable.

I have no use for a cassette player myself, but can't figure out why it won't roll the cassette. I know it has belts, but not being one to work on things, is there an easy diagnosis or way to identify the problem?

When I power it on, open the door, the left pin just spins/rolls. Not the plastic black part that going into the cassette, the metal pin below it. I insert the cassette, hit play, rr, ff, but nothing changes. Belts?

I am going to remove the top (provided it is just a few screws to do so) and hopefully SEE the issue - any other simple/quick suggestions or ideas?

Thanks - Dan