You can try switching but chances how it might not work especially since this animal is already on strike, but you can try there is nothing to lose.

Try offering a rat pup (they are the same size than a mice and it will make the switch a little easier, bigger different prey can be more intimidating), once your BP switches upgrade to a bigger size as needed.

Keep in mind that a 1000 grams BP can go months without food, so simply make sure your husbandry is optimal, keep handling to a minimum and wait till he resumes feeding (sooner or later he will)

Note: When an animal that age stop feeding switching prey type is not always the solution.