Did you put this angelfish in a QT tank? If so, it'll be much easier to get it to eat, without stress from other tank mates. It may take it a couple of days, to feel comfortable enough to eat. That isn't uncommon.
This fish needs a varied diet, including types of algae, as well as "meaty" foods. I'd suggest trying frozen Formula 1 AND Forumula 2. I'd also try some Nori or other algae products.