Does he have a hide? If not you should get two identical, one for each side. Next time try warming up the rodent. After you thaw it at room temp put it in a ziploc baggie and put the bag in some hot tap water for about 30 min. You can also try offering smaller prey. Did you do the all to enticing zombie dance? Hold the rat by the scruff and dance it about 2 inches from his nose. Don't be too persistent with feeding as it can stress him. Only try once per week. If your handling him, stop until he eats. Pretty much leave him alone except for cleaning poop/shed/ water. If all else fails try popping the rat in his hide with him over night.

Hope this works out for yeah, Jeremy.