Unless you have removed a hose from propane pipe or broken loose a fitting on the propane pipe there is no air in system.
There IS a lack of propane flow and no demand on regulator.
Valve in propane
Light a match or your choosing be it kitchen match, BBQ Lighter, book match or cotton ball---stick lite object next to stove top burner
Turn burner on HIGH
When it lights off turn other burners on and light them off.
You have now established the flow of propane and placed a demand on regulator.
The propane system is now at roughly 0.4# (11" WC)
Depending on piping and location fridge/water heater may take several attempts until flow is sufficient from them to light off.