Those are not easy snakes to keep. Probably nothing wrong with it. Try feeding it quail, quail eggs, see if that works. Which species is it? I'm assuming here dendrophila dendrophila? How old is it/size? WC/CB? Any "Customer Support" from the breeder in case of CB?
These snakes can not go long without food. You can't "wait them out", especially not juveniles, they'll just die on you. Force feeding is very common among Boiga keepers when dealing with juveniles.
Join this group on FB, lots of info there:
https://www.facebook.com/groups/160394140730427/
PS. move it out of high traffic area's, they stress incredibly easy.