Install black or galvanized 1/2” pipe to within 2 feet of the appliance and make the appliance connection with copper tube with flares.
I know this doesn’t help with your question. The only thing I got for you on that is, in a wide open area, far away from any source of ignition, use the divide an conquer method, starting at the propane Tank connector. Just run it and see if you get gas flow. Then on down the line, add the regulator and so on. I’m guessing the connection at the tank. Just a guess