Loosen and remove the chain from the sprocket. Run the opener until the sprocket turns in the clockwise direction and stops. Replace and tighten the chain and try it. You will probably have to adjust the up and down limits a bit. Let me know.

I did that but it drives in the down position and takes the limit switch to the end of it's travel so that it falls off it's threaded rod.

Are you sure all the wires are connected on the limit switch assembly. There are three wires. The brown wire goes to the down contact. The grey wire goes to the center limit contact and the yellow wire goes to the up contact. You might also try cleaning those contacts where they touch each other.

All the wires are connected and the contacts are clean.

Found the problem, removed the printed circuit board and took the covers off the relays, the down relay had stuck contacts. FIXED IT ,