For his feeding habits he had most likely been fed mice his whole life so that is what he knows as food. Not all rodents smell the same so if all they ever smell as food is a mouse that is all they are going to eat. Just like with humans here in the states a steak cooking is known to be food but something from say the middle east cooking may not smell like food to us so we do not get hungry from it. A snake has to recognize the prey item as food before it will try to eat it. You can do as I said after the snake is healthy with some weight to switch it to rats which have more meat on them and are healthier IMO for the snake. There could be nothing at all wrong with the rats except that they are not mice... Also you could get some mice and keep them in a tank and get a f/t rat thaw it out rub it in the mouse bedding and then try to feed it to the snake.