Why can't I turn the wheel on my Adler 187 sewing machine? Seems like it is locked up. Needle assy wants to move but doesn't .

Make sure you don't have a bunch of thread from a miss-feed under the cover in the bobbin area where the walking foot is. Or even a piece of a broken needle there that moved.

It won't move forward or back?

As smoothy said, open up the areas you can and check for a jam. Thread and lint collect there like no one's business. All else fails take it to be serviced by a professional.