Congrats on the new gecko! The not-eating and hiding is totally normal for the first week or so—he's just stressed from the move. Give him at least 5–7 days of quiet time with no handling and he should start hunting when he feels safe. One thing that'll help: if you're planning to keep that...
The good news is that he's still alert and responsive, which means this hasn't progressed to the really serious stuff yet. But weight loss from regurgitation is a red flag that usually points to something your gecko can't shake alone—most commonly a parasitic infection (cryptosporidiosis is...