I've had adult pythons out of no were go off there food. Maybe try something different in his/her diet. Works most times for myself. Maybe a bit of chicken get a chicken drumstick or breast and cut a piece of flesh off about the size he needs, make sure it's room temperature and give him a go on that, if he eats than through in a rat/mouse scented with the chicken. I have a incredibly fussy tully jungle that would eat nothing more than pinkie mice and she is a adult so you can imagine how fast she was growing. I tried her on the chicken the other day and she took it with no fuss. Also some snakes just decide every now and again to stop, she could sense that were not that far off cooling could be numerous things but give the chicken a go.