Joe, at one point in time, one of my angels bothered a lot my other angel. Because of this, the bothered angel stopped eating. It would also ignore food. However it luckily went away by itself. What I have read here on fishlore and in other sources is that angels can go on a "hunger strike". They may simply get bored of the same type of food they're getting. If you're feeding your angel with only flake food, try frozen blood worms. Angels love them. Even now when my angels have no problems with eating, they sometimes won't eat flakes for a day or two but when I bring them blood worms they go crazy about them!
If not the above cause, maybe your angel is still not relaxed and not used to its new home. Maybe it's still afraid and needs more time. It also is probably used to living with other angels and maybe it feels uneasy being alone all of a sudden. Though I am sure it would eventually get used to being alone. But! Of course you want to get it some nice friend

(if it won't overcrowd your tank)Well, good luck!
