Often food refusal has to do with husbandry...& you've shared no details so it's hard to help you. We hate to assume...
It's possible this snake is not healthy. You said he was "used to breed"...do you own the female or was he loaned out? Exposure can happen anywhere, & maybe he's sick?
I can recall member & BP-breeder (Deborah Stewart) had said that a half-hour car ride could help. That makes no sense to me personally, but I'm not a BP-breeder so maybe try it?