Sounds like this is live feeding. Was the rat pretty large. Some snakes until they get use to it shy away from rats especially if it is moving around quickly and coming toward the snake. And worse since this is a new environment. I would feed every 7 days being the soonest even if it was refused. Wait 7 days and try feeding a live adult mouse or two. Or maybe you want to try frozen thawed rat that is around 50 grams. But my experience is if he isn't interested in a live adult mouse he just is not interested in eating right now. Has he been eating live or frozen/thawed (warmed up ) ? If you use a live rat try to get one about the size of a huge mouse. 80 grams or less was a good idea stated by Deborah.