will it roll? have you tried shifting into gear with the steering levers pulled all the way back. have you made sure the park brake is disengaged?
Check the easy stuff first. Check shift linkage adjustments and or if something is jammed or broken in the linkage. Possible that transmission clutches are not releasing.
Loosen the brake bands once and see what it does.
The transmission input shaft should turn free in neutral
Most likely you have transmission problems if it was anything behind the trans the input shaft would still turn
Greg