I suspect perhaps the temperture is too low? Pacman Frog prefer a temp of 80-85*F in the daytime, and prefer 70-75*F at night.

You see, Pacman Frogs burrow to keep cool. Down below the substrate is much cooler than above. If it is cold, they often will not burrow. Also, Pacman Frogs are cold-blooded. This means that they function based on the tempreture of the air around them. If your setup is too cold, then they will not have the metabolism to properly diegest the food (which could cause problems), so instictively, they avoid eating when it is colder.

You may want to check your tempretures in the setup, or buy a thermometer if you don't already have one. That may not be what it is, but from the description you gave, it sounds somewhat likely.

I hope this helped, and I really hope your Pacman Frog starts eating again!