Propane Auto Change Over Did not work

Have you ever had the auto-switchover work before on this rig? Sorry if this sounds silly but you do understand that the valve does not physically move during switchover....it merely determines the primary tank. Once you know that the tank is empty...and its properly swapped to full tank you can physically flip the lever, and then disconnect the empty tank to refill. I also suspect that the overflow preventer kicked in and you had a full tank that wouldn't let you have any flow.