First of make sure to check the CARESHEET cause the pet store guys do make mistakes from time to time. Second how old is your snake what size is he? a 40G tank may be a little big for him I would also try covering 3 sides of the tanks to make him feel more secure. But I would make sure your husbandry is spot on and give him a week with as little handeling as possible then attempt to feed him again. Hope this help and be sure to ask if you have any other questions