I will tell you what has worked for me both times Ive had a CBB to get it eating.
Step one. You have its interest in food, now you have to convince it to eat. They love wiggly food worms are part of their natural diet, along with anemones of course. Blood worms are a good place to start, with high flow going to push them around. If you HAVE to get it to eat something Live Brine almost always works.
Step two. Once it is actually eating something, even live brine shrimp, you are getting somewhere. Start to mix in some bloodworm or even better, mysis shrimp with live brine. This will help getting it to attempt to peck at mysis. This could take several days. A community feeding response is best to get it to eat the mysis. CBB are voracious eaters when they are comfy and happy, and they legit get jealous when the see all the other fish eating what you put in. This feeding response has been crucial in my experience.
Step two and a half.
If it still will not eat mysis, try frozen angel and butterfly food. That also helped mixed with Live brine. Also take a clam on the halfshell and rubberband or wedge it into a rock, this will let them peck at something naturally.
Step three. you can buy live or frozen black worms to mix into whatever food you desire, this ususally works. After the above steps with mixing live brine into frozen it usually take only a day or two and they will eat frozen.
Now if there is aggression going on at feeding time, then the feeding response part is null and void, and I believe this is the single most important part.
Some things you can try right off the bat if you have access, just to get it to eat, beside live brine are live black worms or white worms, both will do. Also you can take masstick and stuff it into a rock crevice.