You have a leak.
Get some leak detection fluid. Available at many hardware stores, Home Depot, Lowes, etc.
Looks like this. Rinse with clean water.
Turn on the propane, spray the fluid on the connections and hose (if you suspect it leaking), and it will bubble where it detects a leak.
You could do the same with soapy water in a spray bottle, but, soap is corrosive on the metal fittings. Make sure you rinse it "very" well.
PS
In your pictures, I see white Teflon tape was used on the connections. The white tape is made for water lines, not gas. Your connections should be done with yellow (gas line) tape, or joint compound. I would suspect a leak at one or more of the connections.