It's not uncommon at all for adult male ball pythons to fast during this time of year. I had one that went of feed for over six months once with no adverse effects. I know it is nerve-wracking if you have not seen it before. I have gotten to the point that I automatically just thaw fewer rodents during the winter months, because I expect more refusals, especially from the adult males. I don't worry about them, because I know it is pretty normal and that they should be fine.

If Monty is normally a frozen / thawed eater, offering a live feeder might make him more willing to eat. I have had that work for fasting ball pythons, and then they seem to switch back to frozen / thawed just fine. If he normally does eat live, you might want to keep cage to house the rodent until he feels like taking it if you don't have any other snakes that might take it.