He might just not be used to his environment, it's pretty good to let new fish get used the new home before feeding them. As in, keeping the light off the first day and not feed them for a day or two.
It also depends pretty much on what kind of food the fish is used to from the start, if it was floating food he should realize that food can be found by the surface But just feed him a little at a time and see if he will notice and eat it at all (: He should get used to it sooner or later. If not, you could always soak the pellets before feeding so they will sink a bit at the start, so he'll see where the food comes from d:

You could also try feeding him sinking pellets which can be found at any aquatic supply store.  The slow sinking kind is great and a few will sink at a time and as he gets hungrier and more impatient to eat he may venture closer to the top of the aquarium.  Pretty soon your fish will get over his shyness and when he sees you coming or you opening the lid he will go to the top and beg for food.  Try feeding in one spot every day and he will get trained to anticipate food there.

It's great for the goldfish if you try varying his diet that way! By keeping two-three different kinds of staple foods (: I have both sinking and floating pellets for my fish~
You could also try feeding him some blood worms twice a week, it's a great source of protein! Which is important for younger, growing fish (:

I am sure he will get used to his environment and will start eating from the top surface too.
I cannot give more advice than Kat , Nossie and Mindemae already did.

Please keep us updated

... and don't be alarmed if they eat not straigt away if you give them sth new  they can be fussy too  but in the end they'll eat it.
Only once they sucked me in when I gave them peas for the first time. They did not touch them. So I felt guilty and gave flakes, they gulped them down as if there is no tomorrow. And you wouldn't believe a few hours later the peas were eaten up too, I did not find them in the filter