..is your problem.
Had a propane problem where the OPD valve would not open. Got a tip from youtube I thought I'd pass along.
Usually when I open the valve *very slowly* it will click open, but if not, then I've used a screwdriver on a valve on the side to relieve pressure until it would. They can be overfilled regardless of the OPD. This time that tactic didn't work.
Guy on the tube said to remove the hose fitting, and look directly into the valve and you'll see a metal washer, or valve, that needs to be 'reset'. In other words, it's stuck, and needs to be pushed in and forced loose. I did that with a phillips screwdriver and a bit of WD40, a few times, hooked it up and voila.. good to go. It takes a bit of pressure to actually move it. It's spring-loaded.
About an hour later it was closed again, so I repeated the above and overnight it stayed open. They guy said to open the valve a little bit first, but I didn't see the need for that as I really didn't want cold and highly flammable gas spewing out at me.
"If I'm wearing long pants, I'm too far north" - 2oldman