The only thing I can suggest (and I haven't had my morning cup yet either) is to take a small frozen rat maybe 40/50 grams and put it in a bag with frozen mice. Put 2 or 3 frozen mice in the bag with them all touching and laying together. Keep that bag at least 3 days in the freezer. This is done to get the smell all entwined over each other. Then when time to feed take out the frozen rat, thaw, heat and try to make the rat seem alive. Grab it by the mid-back and make it wiggle or tremble, walk it past the hide door, in other words try to fool the snake in every way, smell and in action.
But it might be you have to stick with live mice. I had a snake like that. It hated rat. Some say tough love works and that hunger eventually wins. Maybe so. Some say just feed them what they want. The decision is up to you I guess. Glad I only have one and it eats f/t rats no problem or hesitation. I used the above method to get mine from mice to rat.