Are you sure the crickets are being eaten and not just crawling into cracks or do you use a bowl to feed? Is feces appearing?

As long as food is being turned into poo, I wouldn't be concerned by apparent inactivity.

Higher humidity could be a cause- if it is able to stay hydrated sitting on a leaf then it has no reason to move to a water source. This would also not be concerning.

Also, you might want to specify what species you mean by "Green Tree Frog". edit- I see from your albums it's a Hyla cinerea.