The shadow is not really the problem. They love full sun, but can stand a lot of shadow. The lack of water or nutrients may be. Let it fully submerged in a bath for one hour. If is still alive, the bark or stems will turn greenish and new leaves may appear in a few days.
Sinense is semi caducifolious (if I remember correctly). Are you in spring or in autumn currently in your timezone?
(If you have pets take in mind that this is a poisonous plant with poisonous fruits only allowed for birds).
It was still trying to live off its two remaining leaves, when I picked it up by its trunk and noticed it was completely hollow and almost made of paper. It was utterly desiccated.