sometimes the manufacturer does screw up. i have a new bianchi holster, belt model, thumb break with the same problem, almost half inch too short from the factory so the snap will not engage. true factory defect, not sure what i will do with mine.
it looks really extreme in the photo, so not sure if mink oil is enough. made some decent leather holsters in my younger days when i had too much time and ambition. return to seller, or you can also try if all else fails:
- soak the female snap end in serious hot water, put you gun in plastic bag, put the gun as tight as possible into the holster, and grip the part you are stretching (even using a vice clamp plier), stretch the hell out of it to the part the snaps take hold, keep it snapped in place overnight. the plastic bag keeps the moisture off the gun overnight.
(having no gun to mold the leather, i used to soak the whole holster in hot water, stick the gun in a plastic bag, use a boning tool to get the outlines, and let dry thoroughly, than apply the leather oil and finish, did not harm the gun or the leather)
- another option is to check any room in the holster area in front of the trigger guard, take some stitches out which moves the gun lower so the thumb break will work, then rivet or restitch to keep the threads in place
- final option is to cut the top part, so no thumbreak and it is converted into an open top holster
good luck