Hey,

The tank is far too small for activity and thermal and UVB regulation. A 18 x 18 x 24" is the absolute minimum for this species due to its size. Give him a heat light during the day to bask at 85F and UVB is beneficial, about 5% in the tank I mentioned. Once these conditions are provided and the frog still refuses to eat you could try getting another frog. This will give it more competition for food and may encourage it to eat before the other frog does. They also do seem to enjoy the company and may spend time near or cuddling with a "friend"

Hope this helps and Merry Christmas!