When it has been turned off for a while, you get air in the lines, don't ask me how. Hold a match to the burner on your stove and turn on the gas, hold the match until the air is purged and the flame lights and becomes consistent and stays lit. Tip from an RV tech. Used it many times.
Also when you first turn the gas on at the main valve it flows so quickly it may think there is a line break and a safety valve highly restricts the flow. Give it a few minutes to equalize pressure both sides of the valve and automatically reset the safety and you will have gas pressure where you need it. You may still need to purge the air.
Another tip: Propane is odorless, so the distributor adds a smell agent to it. One possible smell agent makes a propane leak smell like a mouse died two weeks ago in the hidden recesses of your rig. Dead animal smell rather than the familiar rotten eggs smell we associate with a gas leak. It is beyond me why anyone selling propane to an RV'er would use that smell. My recent experience with that: http://www.irv2.com/forums/f258/some...en-329286.html
Ole and Anne Anderson, Highland, Michigan
'02 Adventurer 32V, Ford F-53, ours since 4/08,Goodyears, Konis, SeeLevel, CHF
'84 CJ-7 , 5.3 Chevy, 3" lift, 33's, Detroit Locker, Fiberglas tub, winch, hi-lift