Do you always stay and watch? My BP will generally not eat if I am watching, so after I put the frozen/thawed rat in his tank I turn off the light in the room and close the door, come back 20 minutes later and he has eaten and is asleep in his hide.
I have tried a few methods of thawing and he refuses slow-thawed rats like under his heat lamp or using just warm water. What he prefers are rats thawed in a mixture of hot tap water and a little water from the tea kettle which thaws a weanling or small rat in about 35 minutes, I change the water halfway through since the water cools too fast sometimes. I use a ziplocked bag to try and keep the rat dry but water still manages to get in the bag, he has never minded eating his rats wet thankfully.
However, his favorite is freshly killed rat, my local reptile store (which is 15 minutes away) had no frozen in stock one time so they killed some for me right then and there, I decided to give one to my boy right when I got home and he came out of his hide with more enthusiasm than I have ever seen.