The Float optimizer must be unlocked "in Flex" to calibrate. If you lock the head rigid, the sensors cannot travel to calibrate. IDK if locking the wings would have any effect. The best way is to raise the gauge wheels out of the way, unlock everything, and calibrate on a flat level surface. I think it would also be possible to calibrate with the wings locked and wheels down, it would just require more care and knowing what you are doing.
What you are calibrating is the "travel" in the float optimizer frame. So the better job you do keeping everything level during Cal, and only letting the float optimizer travel in the normal operating range (see blocking comment), the better the control system is going to work in the combine.
The other major problem we see is trying to Cal with the Float springs so tight the head "Floats up" when you raise it. This completely confuses the combine cal function. You must have the head hanging all the way down on the float optimizer when the head is raised all the way to the top. If it floats up or even bounces up pretty good, you are going to have to loosen the springs during CAL (or add weight. Sometimes running the reel clear forward is enough!)