I had an adf last year as well, and he would not touch the pellets. He literally starved to death in months.
Now I have 2 in my 10 gallon, and feed them frozen brine shrimp/bloodworms. I've had them for weeks and they wouldn't touch the food. But today, one of them finally ate.
Be sure to put the food right in front of their nose, as they have a terrible sense of sight/smell. But if your frog still doesn't eat for a couple weeks, I suggest getting some frozen foods. A lot of adfs just won't eat pellets..