Ya you can't just open the vavle and think propane will come out.

But if they ran it up til the auto shutoff vavle closed when filling the tank. then the overfill vavle may be stuck shut.  Have to let some out and tap on it and see if it will free up.

I try and shuter down before  the overfill vavle stops me from filling the tank.  I don't think it is good practice to let the tank shut off the flow all the time.  I know some do though.