The pin I spoke of was part #100 below. The hydraulics of the lift cylinders are connected to each other. Unless both are physically connected to their "load" the connected cylinder won't move the load and the hydraulic flow diverts to the loose one and it will just go back and forth in the air.
When I reinstall the loader, I usually stop short, connect the hoses, then drive in closer. At that point I pull the stick as you would to raise the loader. The two frame sides rotate toward the tractor to meet the two main frame pieces on the tractor. Frequently the movements of the two cylinders are not exactly in sync. After the first one contacts the main frame, the other moves till it also touches its main frame.
Then dumping the bucket drops the frame sides into the main frame. A little more rotation or a little down pressure on the loader lifts the front wheels. At that point BOTH! #100 pins go in (not just ONE as I did) and the two stands can be raised and pinned. Next the loader is lifted and off you go.
in my case with the right #100 pin not installed, the right side of the frame jumped out. With the stands already in their stored position, the hydraulics couldn't help me. The loader was sitting too low to allow the stands to be rotated into their lowered position.