Drop the temps. I keep mine at an ambient of around 77-79 throughout the cage. He has one small spot at the back right corner that has a little Nano CHE and a t-stat set to 85F. GTPs generally dont like it really hot. At least he isnt grounding so you got a plus there.
Second, dont mist the snake. Most babies hate being sprayed with water and it can piss them off or stress them out. I personally never mist my cage and im using a Zoo Med 18x18x18 cube. I just cover the top with tin foil and leave a hole in the back right corner for the CHE. I use Reptichips on the floor with a large water dish and a live potted plant. That keeps humidity around 65-70%. You dont want a constantly wet cage. That will create RI conditions.
Also give us a pic of what you got. The snake might not feel secure. Pat LOVES plastic plants so i have 4 of those in cage which he will sleep next to and play around on all night long. It's a good sign he is at least exploring at night.
When you offer him food, are you just touching him? Sometimes you have to kind of smack em around to get them good and pissed lol. Also you can try and pinch the snout of the pinky mouse to create blood.
Also is the snake drinking? A dehydrated snake wont eat. Again, need to see the set up. Do you have elevated water bowls? Have you seen the snake drink? Are you injecting the FT with water?
Neonate GTPs really arent that hard from what i have seen but you need to get it right. There is too much that can wrong if you dont know what you are doing. But otherwise, to me, they are as easy to care for as my BCI boas.
To give you an example, here is Pats cage. I got him about 3 months ago when he was about 10 inches long. He was a little bit of a problem feeder for the gal but now, he is about 20 inches long and eats like a horse every 5-7 days. After about the 4th day, he is out in force at night looking for food or perched at the front of the cage staring out the door lol.
Also, if i didnt emphasize it enough, you need to make sure the snake is drinking. They use liquid to digest food. They also lose liquid to too much heat. They also piss out liquid. And neos will dry up quick. Try and hold a little tiny bottle cap of water to the snakes face during the day. It might drink. Pat drank water that way at first. Then he figured out the elevated little water dishes and found his large water dish at the floor which he swims in pretty much nightly. I still inject his FT fuzzy mice with water though to make sure he stays hydrated even though i have seen him drink.