My king has always been an extremely shy feeder, which is kind of odd for a king snake. I have to leave the f/t feeders on top of her hide and walk away, she'll only eat in privacy. It's been 9 years and she's always been this way (she also likes to hide under her water bowl which is way too small to actually hide under haha).
I've used the brown bag technique for non-feeding hatchling corn snakes and it is a great trick.
OP, I hope with the great advice you're getting that your lil one will be chowing down in no time.