Ok, first try what the post said above mine. That is how my burm eats her rabbits, and how I got her to finally eat dead. But give it some time, what I mean is, do not try this everyday. I would let your snake go 7 to 10 days without feeding it, then try warming it up and try offering it on tongs. If that does not work, try this. You will have to go with pre-killed first. I found this to be the hardest thing I have ever had to do, but it worked. You are already ahead of mine because it is eating. So, take a mouse or whatever it is eating and put it in a pillow case or bag and smack it, wait till it stops kicking and then offer it on tongs. After about 3 weeks or 2 weeks go with the warmed mouse. I bought a bucket for this purpose. I use hot water from the bath tub in the bucket and put the bag in there and let it sit. It gets warm I offer it and she nails it and eats it. If it is still cold she will not hit it or will and then leave it, then I just have to warm it again, she is spoiled. Also you might be lucky, my boa use to eat frozen from tongs now I warm them and just leave them in the cage and she eats them. You can try just to leave it if it does not take it from the tongs and come back in an hour, and see. I have tried the braining the chicken broth, and none of those worked for me, but some have gotten it to work.
Keep us posted
Jeff