Like Grif said, answer the Trouble in the Enclosure questions. But you should replace the moss with cocofiber (like EcoEarth). If they eat the moss by accident they can become impacted and die.

If everything is correct husbandry-wise and he has no other issues, he may just be used to eating that way. I had to rub food on my frog's face for months to get her to eat while she was recovering from an illness, and now she won't take food any other way.