If his husbandry is on point and he otherwise seems fine, I wouldn't worry too much. It can take a while for a ball to settle in...I bought a female(900 grams) a couple years ago that didn't eat for the first 10 months I had her, and she was provided with proper temps, humidity, and even a hide which I don't normally use at all. Just keep an eye out for rapid weight loss, that would indicate a problem.