You are opening your propane tanks too fast and tripping the leak shutoff valve.
Close your tanks and wait for at least 5 minutes. Then S L O W L Y open the valve. It should take about 5 seconds to make that first revolution. This will allow the gas to slowly pressurize the gas lines and prevent the safety device in the pigtail from closing.
If you are still having issues after doing this your pigtails are bad and will need to be replaced. DO NOT "blow them out" with compressed air as you will destroy your regulators (don't ask how I know).
Search on "red regulator" if you are curious.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW