Pics of the frog and tank may reveal something, but as always, a vet visit with fecal exam is usually the best course of action.
Posts some pics and someone might see something to help.
What are the day and night readings of humidity and temps?
What is your water source and what are you feeding? Are you providing supplements?
When was the last time you know the frog ate and when was the last time you found fresh droppings?
My RETFs are very selective eaters and don't gorge themselves like a Whites Tree Frog does. Mine even take turns during the winter months of which is active and which isn't. Sometimes one of mine may not move for days even. Also, drastic or fast changes in barometric pressure will effect the activity level of the frogs.
If the frog was healthy, it can go for quite some time without a meal but any time your concerned, its best to get to a vet.