I would just say keep at it. I hatched out 11 babies last year, and 10 converted readily from live mouse hoppers to live rat fuzzies to f/t a few weeks later.
The 11th had me tearing my hair out - if he wasn't offered a live mouse he showed no interest in eating, and often hissed or threw coils as he scurried under his hide. This was every week until last week. I was feeding the others their f/t rat pups and he was up at the front of the tub acting hungry, so I offered him one... and he ripped it right off the tongs. The only thing I can think of is that my supplier didn't have live small mice so I was feeding hoppers - and he finally got hungry enough to go for a different feeder.
Be patient and keep trying, he'll switch eventually.