Propane Auto Switch Over Valve

[BB_TX]

We got our Monty last summer and have done very little cold weather camping and have not used much propane. I seem to have a problem with the switchover valve. If I point it toward the curb side tank and open that propane tank valve (leaving the street side tank closed), the switchover valve turns green. But if I point the switch to the street side tank and open that tank valve (leaving the street side tank closed), the valve remains red and I get no propane to the camper.
If I bring the street side tank to the curb side and point the valve back to the curb side, when I open the tank valve the switchover valve turns green immediately. It seems as if the valve is not switching to the street side.
Both tanks are full.
I think it worked last year. Last Sept in Colorado it was cold at night and we used the furnace in addition to cooking. After a few days, I noticed the valve was red (pointing to curb side) and I seem to remember switching it to the street side and it turned back green. Been a while, so I am not now really sure. But we never lost propane to the 5er.
Do I understand the operation correctly?