Tank is equiped with a line burst valve at the tank. Safety feature in case of accident. If the tank valve is opened too quickly it trips the line burst portion of the valve.
Shut all the propane appliances off , then shut the tank valve off and re-open the valve VERY slowly. Back pressure in the system keeps the line burst feature from tripping . Opening the valve quickly will trip it.
Hope thats all it is.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.