Loosen and retighten with a good quaility wrench or flare style wrench . There is no torque spec. Tighten until no leaks.
It is possible you may have to dress the metal line end with sandpaper carefully if it has a buildup of crap on it.
legend in my own mind
Advice is only as good as the person applying it--
Don't make me give you bad advice!
Lemons or lemonaide, whatever your taste provides.