I don't know about box turtles, but it often takes a RES several days to settle down and start eating after a change in habitat. Maybe your guy is just nervous because of the changes. In any case, there are tricks we use with RES to entice eating. Hopefully someone on here with box turtle experience can give you some guidance on what works for the boxies.
Your turtle is stunningly beautiful, by the way. So colorful.



