D21 stuck 3 point

Position Control and Traction Booster levers need to be fully forward for full lowering of the hitch. The front outside (towards fender) lever needs to be wired fully forward. Then, apply down pressure on the arms. You might try a log chain around the draft arms out near the end and hook down low onto something heavy and give them a jerk to start them down. Those old style lift cylinders seem to get stuck in the "up" position when left that way for years. You can prove it to yourself by disconnecting (or loosening a lot) one of the hoses going to one of the rams. I'll bet they still won't go down on their own even with a hose disconnected.