stress and temps would be the first 2 things i would recomend ruling out.Stress can be caused by the animal being in 2 big an enclosure or by it being handled to much or constantly annoyed so thats something to address then temps are equally as important,to high a temps can make it a little aggressive but to lower temps will put it off its food.I have a 8month old murray thats eats no problem.He is in a 2foot tank with a heat mat and basking light and a uv fluro which is on a timer.My temps remain reasonable consistant at about 32/33 at the hot end and about 25/26 at the cool end.I would suggest to perhaps leave him/her well alone for the next few days to a week almost forget you have it then offer a completely thawed mouse which has also been warmed a little using warmish tap water.One last thing is mine will not eat wet or cold mice so perhaps try thawing using a zip lock bag if you defrost using water and maybe try warming as mentioned hope all goes well and keep us informed cheers Troy