I assume your feeding F/T?

I would try live to get him on a regular schedule then swap back to F/T or P/K when he is eating consistently.

Also, if you are feeding F/T, make sure that you are heating the rat/mouse up enough and that it is thawed all the way through. Biggest thing I could suggest, is just try something different. If you are thawing in water, then either slow thaw on the counter, or dry the rat first. Make sure your not offering too big or too small of a meal. You could try mice instead of rats.

BP's can be picky eaters. Sometimes it just take finding out what they like to get them to eat consistently.