First....there is NO compressed air.
Propane cylinder has liquid propane that 'boils' off to a vapor. That is all that is in the cylinder---liquid and vapor
Second....New pigtail hose.
Does it have a big GREEN knob for attaching to cylinder?
The ACME nut (green) screws onto service valve ......when properly connected it opens a spring loaded valve inside the service valve. If not fully tightened down the 'nub' inside ACME nut will not open the spring loaded valve and no propane can flow out
Also IF you open cylinder service valve too quickly an excess flow check valve inside the ACME nit will trip and greatly restrict propane flow out of cylinder.
Close cylinder service valve.....wait 30 seconds.
Then SLOWLY open service valve.......listening for a 'click' then you can fully open service valve. (The click is the ball check valve resetting )
And unless you changed out your cylinders they are most likely 30# cylinders (7.1 gallon) vs 40# cylinders (10 gallon)
Just side note.........when pigtail hose broke. The ball check valve should have tripped restricting propane flow out of broken hose.
Surprised it didn't....must have been pretty oiled up---dirty