Pin? What pin?
Sorry Genexsis,
The pin that the cylinder spins on. Sometimes they back out and tie up the cylinder. It's a matter of screwin' it back in...and unless your revolver is unusual, it's got a left-hand thread. It'll probably back out again unless you put a little lock-tite on it and tighten it up pretty well. Use a leather or heavy denim strip on the knurled end to keep from buggering it up, and use
pliers to tighten it. Don't get too carried away...Those threads are small and will strip if you put too much torque on it.
I sounds complicated, byt it's really not. It's just hard to write out step-by-step instructions in one paragraph. The hammer block only goes in one way, and there's a slot in the sideplate that it has to ride in. The top
of it goes in toward the left side of the gun, between the hammer and frame. The slotted end goes over the small pin on the rebound slide, and the sideplate slot fits over it. It'll make more sense when you get it out.
If the latch is gummed up, spray it with WD-40 to wash out the gunk, and let it fry for an hour or so...then put a drop of fine machine oil in the mechanism...Sewing machine oil will do, or household 3-in-1 is pretty good...or Marvel Mystery Oil will also work. just a little goes a long way.
Since the problem started suddenly, my guess is that the pin backed out.
There may not be a need to take it apart.
Luck!
Tuner