You are not trying to feed the snake every day are you? If so, don't, you could be stressing it and that could be why it is not eating. Only offer food once a week, and try to do it at night, you will most likely be more successful since they are nocturnal. Also, if you wanted, you could pre- kill the mouse/ rat and leave it in the cage over night, I have had success that way as well. If you do not want to pre- kill, then you should make sure the mouse/ rat does not touch the snake while in the cage, it kind of freaks them out, then they usually won't eat.

I know you said where you got the snake from they fed it live, which is fine, but do you know if they were feeding mice or rats? There is a big difference if you are trying to convert over to one or the other, and it is even harder to convert over to frozen thawed.