I have an enchi I hatched out that was refusing to switch for the longest time. I finally left a rat pup in a small critter keeper with a mouse and some soiled bedding for an hour before offering it. I also scented the room so he was ready to hit immediately when the tub opened.
Oh and you think that's bad, my female baby rescue retic decided she was going to be stuck on LIVE mice for a long time.She finally took a live rat a few weeks ago. Now to get her onto f/t.