You never said one way or the other about the mice the previous owner fed; I just wanted to cover the base, just in case. As far as interest, I let mine thaw to room temp in the room with my snakes (on top of the cage, if it's a tank). Then, blow-dry the head of the rodent for ~30 seconds to get it good and warm, and get the scent going well. My BPs are so conditioned after just a few meals that they automatically poke their heads out when that dryer switches on! Offer with tongs, holding it by the scruff about 3-4 inches from his head or the front of his hide. If he doesn't strike, just leave it in front of the hide entrance. If he's eating, then it sounds like he's plenty interested in his food, it just takes him a little longer to get hunting, or he's shy.