More than likely hes not eating due to stress, or husbandry issues you may not be aware of. I personally think a 20 gallon tank is too big for his age but can be made comfy for him with plenty of hides and clutter. All the constant roaming is definitely a sign that hes uncomfortable. Be sure to triple check all temps regularly, also keeping the enclosure covered will help him feel secure. 2 missed feedings is really nothing to worry about give him time and fix all enclosure issues (if any) and he will eat.