If he won't eat frozen you should try live if that's what he was eating and try to transfer him onto frozen after a few feeds.

You can of course try frozen and he might take it, but it's there to let you know why he may not eat. BP's can be fussy eaters at the best of times. Some will eat anything, at any time. Others can easily go off food by the slightest change.

Hope he takes F/T for you