It's not uncommon for a lot of fish to not eat when put into a new environment. In fact, I prefer to try not to feed at all in those first couple of days unless I know they haven't been fed in the shop. A hungry fish is a healthy fish (so is a hungry cat, but that's another story) as I was taught by the old-timers, so waiting until they're settled allows them time to decide whether or not they have an appetite.
However, I'm going to guess that you've tried to feed and it's not. If it appears otherwise healthy, check your water parameters, pay closest attention to ammonia and nitrite levels. If those are readable at all, then a small water change may be necessary.