I have had my blue jaw now for 2 years. when I first got him, he stayed in quarantine for close to 8 weeks. It took him a whopping 28 days before I actually saw him eat, he would just hide. I got to the point where i would feed, and then hide for up to a half an hour before I finally saw him come out and eat. Now, he's one of those fish that I can literally pet when I feed the tank.
Just a very shy species, be patient and continue offering food. they are water column feeders so mysis is a good bet. It helps if there is circulation in the tank to keep the food suspended in the water column as well.
Good luck!