what is your thawing/feeding method?
Far from expert, but I followed the advice to the letter in this thread (corroborated by some additional youtube videos) and it was very successful with my youngster:
He had never eaten frozen thawed, only live. Though this is my first ball python, I’m pretty experienced with a variety of other animals and typically, it’s really helpful if you truly set up an animal for success with no excuses in a way that follows their natural instincts right from the beginning whether it’s a dog, cat, horse, or snake 
I only feed after dark, like 9pm+. I thaw out the rodent near his tub so he can smell it in a small container. Once it’s thawed (up to room temp), I then heat up some water in another slightly larger container and put the smaller container inside (so the rat doesn’t get wet). I lightly dip the rodent’s head in the hot water so he keys in on eating it headfirst and use my temp gun to determine when it’s up to normal body temp. I have one small lamp on so I can see in the tub to offer it, but it’s mostly dark which helps as well. I also do not handle him the day of or for two days after so as not to stress him out and to not associate handling + eating/accidentally tagging me 
I think in general it seems to be advisable to not handle them much at all if they’re not eating consistently and to have them in a smaller, darker tub than you’d initially think is necessary so they feel secure and comfortable.