If the animal was indeed feeding on F/T (which means had more than 5 consecutive F/T in the past with the previous owner/breeder on it's own) you do not want to offer live just yet unless you are willing to do so for an extended period of time.

You also do not want to offer next day after a refusal, when you have a refusal you offer a week later, offering too soon can lead to more refusal.

The key is appropriate size prey, already established it is not even if it was fed this previously.

optimum husbandry. 99% of food refusal in new animal arriving to their new owner is husbandry related.

How big is the snake (weight?)

How big is the enclosure?

What type of substrate are you using?

What are your temps? How do you measure them? (where and with what type of thermometer)

How tight are your hides?

Have you been handling your BP since it arrived/was purchase?