Were there places at the store for the fish to hide? How/what is the fish doing now?
Just like people have such different personalities, individual fish can differ from the average species. I have a magnificent foxface that is PTSD level shy still after nearly a year. It will come out and swim if 1) no human movement in the room and 2) swim with another fish... but my 180 only has a few fish. I do wonder if it would do better with even more fish, but I plan only 1 more and not for a while (but... plans are made to be broken - lol)
Hoping this note finds you and your fish instead having settled in and started swimming freely within your aquarium. Please give us an update when you get time.