In either case, has the BP fed for you before in that enclosure? If they are in a brand new environment, it's sometimes too much to try and introduce a new food type right away.
The most successful methods seem to be first perfecting husbandry, letting it settle in a week with minimal interaction, feeding it whatever type of food it was eating prior to you obtaining it, then once it is consistently feeding for you, introduce the new food type.
If that isn't possible, it's probably even more critical to make sure the setup is perfect and stresses are minimized.