I haven't kept one in a while, but I recall them being both shy and nocturnal. If you're not already, I'd suggest dropping in something that sinks (i.e. shrimp pellets) when the lights go out.
If he's found a spot, he's probably fine. What else do you have in the tank? I have a lot of livebearers and omnivores, so even if I didn't see mine eat, I was pretty sure he was getting food since everyone in there was getting a mainly veggie diet. You could put some cooked zucchini near his favorite spot and see if he goes for that.
i have 2 angels 4 mollies 4 neon tetras 1 dwarf gourami 3 spotted plecos 3 corys
They are shy during the day but will attack other fish at night, they are jerk so watch the tank mates, as far as eating in sure he is you just aren't seeing it, does his stomach look sunken in?
I don't have angels and I only know them from youtube really, but I always get my mollies excited over something one side of the tank (seaweed, pellets, food, whatever) and then give my shyer fish their foods on the other side.)