Be aware that there can be a excess flow valve in the pigtail that connects to the tanks..
HERE"Marshall Excelsior MER401-12 Excess Flow Pigtail 12 in Excess Flow Male POL, 7/8" Nut and 1/4" Male Inverted Flare connections. 12" HOSE Flexible thermoplastic UL and CGA approved hose. These hoses are rated up to 350 psig working pressure with a 400 pound pull test rating. Warning: An excess flow valve will not activate if there is a break or leak downstream of the valve that does not equal or exceed the closing flow of the valve or if the excess flow valve installed exceeds the flow capacity of the system. Each hose comes with two ends and fully crimped brass ferrules"If if equipped with the valve it may have tripped or failed.. I don't know it is self resetting.. May have failed on both pigtails.