Not sure whether the problem is that the control lever becomes disengaged, or the implement disengages from the PTO shaft. If the latter, the implement should lock onto the PTO shaft, but (1) you need to align the grooves on the shaft and on the implement by turning one a little bit, and (2) as you push the implement onto the PTO shaft you need to pull the locking ring on the implement shaft toward the rear. Pushing forward at the same time you are pulling the locking ring back isn't easy, but when the implement shaft is in place, you should hear a click.
