Keep the sides covered day and night. Just use some construction paper. After he's eaten for a week or so, then you can try opening up one of the sides. Like I said, try reducing the amount of crickets in the bowl to 1 or 2, bowl feeding shouldn't be intimidating, but less crickets may make him feel more comfortable. If they're too big, he probably won't eat either. What kind of bowl is it? If the opening is narrow and they feel like they have to climb in, he probably will not go in to eat. QT style set up is important at this time. Get rid of the eco earth and the moss (in fact, you should never really need the moss.) Have you found any feces? Were they formed? Runny?

A fecal test would be really important also right now.

Do you have a current picture of the frog?