Your newly acquired frog needs time to acclimate and settle in. Having a setup designed around a tree frog's needs is a must to giving them a safe, secure feeling home. This means having tall broad leaf plants such as pothos, bromeliads, or Snake Plant. It also means that you need places for them to perch up high and stay off the substrate since they are tree frogs and not a frog that spends any time on the ground.

What are the humidity levels in the tank? Temperatures?

Your tank should also be placed in a quiet place, away from loud noises and outside the tank distractions.

What are you feeding? Crickets are the main meal for these frogs and the crickets should be no longer than the distance between the frogs eyes. The crickets should be dusted with a calcium supplement routinely.

As for sphagnum moss, it works great for retaining moisture but is an impaction hazzard to your frog. WTFs are not graceful when eating and miss often when diving for crickets and once something enters a WTFs mouth, its swallowed. The sphagnum moss is easily swallowed but will knot in the frogs stomach and block the frog up or become stuck when exiting the frog. Pulling a 5 - 6 inch pice from the frog is not fun for you or the frog.
I would use the sphagnum moss under a layer of Eco Earth and have them seperated with substrate screen or windows screen material.

Finally, your frog needs time to settle in with the proper temps, humidity, and accents to feel at home. Limit the amount of times you enter or change things, feed on a routine schedule, mist often, and let him relax.