Angels are mainly benthic eaters. This means their normal behavior is to find food among the rocks and substrate and not in the water column. They eat a lot of algae, coral polyp and sponge in the wild.
If you would like to try live food, try getting some live clams from your local grocer with a sea food counter, popping one open and placing it in a tight spot in the rock so it doesnt get blown away. Another thing is there is a type of food called mastic. This is like a playdoh fish food you can press onto the glass, but even better, press it into a crevass in a rock and it will mimic the fish's normal feeding.
I currently have a majestic and eibli angel in my tank and both are eating nori on a clip and LRS Herbivore Frenzy as well as pellets from the water column. I had a bicolor a few years ago and his favorite food was my LPS coral. Keep offering different foods in different ways. Four days is still new for a fish and some take a while to accept food.
