Another place to check: the pigtails also have a safety valve in them. If all the aforementioned checks have failed to discover the issue, you could try turning off the gas, disconnecting the pigtail at the tank, tap the pigtail on something hard a couple times, reattach and open propane valve SLOWLY (like stupid slow) and test again at the stove keeping in mind that some air will need to be bled from the system.
I have actually had to replace both of the pigtails that came with my trailer. The first was under warranty and sprung a leak. The second was a few weeks ago, and was more preventative because the visible rubber parts were beginning to look cracked.
2014 Jay Flight 28 BHBE
2015 RAM 2500 6.4L HEMI, Tradesman 4x4, 3.73
Blue Ox SwayPro (BXW 1503)
Upgraded from an REI internal frame backpack and a Eureka 1/2 dome tent!