wow,. juvies should eat daily... it might be caused by stress.. i would leave him/her alone with a few prey items and see what happens.. if it doesn't eat by tomorrow i would explore the possibility of other options ie: getting a hold of the breeder for a refund/replacement, or seeing a vet that has some chameleon experience..
Originally i thought the thread read 4 MONTH ..at 4 weeks this could be really bad news.. did you raise the clutch? or did someone actually sell you a month old hatchling?