This sounds like a tree that may have gone dormant, as many tropicals will do, if they get stressed. (Serissas, Jaboticaba, and Texas Ebony come to mind.) A lot of these seem to be dead and are prematurely discarded.
Many times, the best thing to do is just put it in a protected corner of your growing area, and water it lightly, keeping your fingers crossed.
I have a Texas Ebony that got missed by my house sitter in July. Still passes the scratch test. Still looks dead. My fingers are crossed..........
