The infamous hair dryer trick does it for my BP. I thaw it in slightly warm water for a while until it’s soft all through (you can squeeze it and feel if there are any frozen parts left) and then once it’s entirely thawed I pick it up with long feeding tongues and give it a good blast with a hair dryer to raise a temperature. My BP has always taken it within 5 seconds of me putting it in the tank but if yours doesn’t just do a lil dance to pretend the rat is alive.
PS I usually warm the head up a little more than the rest of the body to help my BP with taking it head first causes boy he used to struggle with that lol