As mentioned, it is usually not hard to get a ball python to switch to frozen/thawed. 8/11 of my snakes will take f/t on a regular basis. The other 3 can be picky sometimes but most of the time will take f/t. I would feed live for the first few feedings then try a f/t. If he doesn't take it, then you could try pre-killed, which would still be warm and have a heat signature that is normal (head and chest being warmer than the rest of the body). Then you can try f/t again.