After changing out the propane tank once I turned the valve on the tank quickly and It triggered a valve that was built into the fuel line and stopped the flow of the gas . What a time I had figuring that one out.
Also spider webs can interfere with fuel flow. I had that issue recently and my water heat was acting erratically, blowing black smoke. I just ran it on electric until I got home.
Normally before each trip I use compressed air to clean out the fridge chimney and fuel chamber and water and furnace tunnels.