Don't panic, it's normal for ball pythons to go off feed for months at a time occasionally. Some of mine do this every year. Keep an eye on his weight, they can go for a few months without food with no problem but if he starts to lose weight then you may need to take new measures to get him feeding again. For now just try to offer every other week so you don't waste too much food and be patient, when he gets hungry enough he'll start eating again. If you do get to the point where he is losing weight, you may want to try live just to bring his interest back and usually once they eat once, you can switch back to f/t again and continue feeding as before.