This is extremely common for new fish. He could just be stressed from moving and trying to get adjusted to his new home, he could maybe not be hungry, or he could just not like whatever you're feeding him because it's different from what he's used to.
But you don't have to worry. Even if he won't eat, just keep providing food at feeding times. He won't let himself starve. When he gets hungry enough, he'll eat whatever you give him.
That is, as long as this isn't because of sickness, but because you just got your fish I'd guess it's probably just the new environment and such.