Don't have a real great answer but the new propane tanks (last 5 years
or so) have some sort of device in them that prevents "excessive flow"
& shutoff automaticaly.

I think they're supposed to shutoff for a broken supply line but i've
had problems with them just lighting up the BBQ; maybe I turned it on
too high to start.

Usually just shutting everything off & starting over gets the whole
thing working again.

IMO it's just another case of the gov't trying to save us from
ourselves, I like the old style tanks just fine.

cheers
Bob