Ball Pythons are notorious for being picky eaters!.. Trust me I have one..lol
When we got our girl she was eating very routine and on a schedule and then for some reason she stopped eating for like 8 months. I was worried but did my research. we finally got her to eat again and all was well in the world...
what I did was:
Offered her a rat on a weekly basis at first, then moved to monthly after about the 4th month.
when she was in her "off stage" we went from frozen back to live with no result, and then went to fresh kill. (after she refused the fresh kill we froze them so we were not wasting them)
make sure she has water and the tank and humidity are at the right temps/levels
check her for mouth rot, it is usually in the corners of the mouth and it kinda looks like the crust from scaly leg mites. also check her for mites
my ball is a female and is over 5 feet long and has the girth of a baseball (NOT soft ball)
it is also the winter and slowing down in eating is normal for this time of the year.. yes they cant feel the cold but they can tell the shorter days.
Gerbils are a favorite of ball pythons but you have to be careful its like giving them chocolate.. and it can be hard to get them off gerbils once you have started
some breeders have had luck with a frozen rat that has been thawed and then re frozen.. the freezing of the rat makes the red blood cells burst.. so with the thaw and re freeze and then thaw again.. the smell of the prey is stronger.
I would also try getting your feeders from a different place... this may sound funny but there is one feed store i cant buy my feeder mice or rats from because none of my snakes will take it (I have 4 snakes) I dont know what it is about the place.. maybe the stock is old.. maybe its they way they were killed (gas apposed to a swift wack) I would ask your feeder guy is he has changed his source for feeders/live feeders.
if i think of more i will let you know but this is just off the top of my head.. feel free to PM me