What's wrong with pine tree?

Norfork Island pines do not like to be wet , I think that was the problem. Not expensive , I suggest dumping it and buy a new one next Christmas and don't give as much water . I had the other problem , after a couple years it got to big for the space ( and still had some Christmas glitter), I gave it away and may get another.

Here are some general steps you can take:

Pine tree's like full sun so keep it near a window where it will have a consistent source of natural light. They like moist soil but not wet soil. What I mean is they desire constant moisture but take care not to swamp them out. One trick for consistent growth is to rotate the plant every other day. It will help to ensure that all portions of growth are receiving and equal amount of sunlight. Be sure to prune it consistently by removing dead old-growth as needed. Also, don't be afraid to feed the plant with a quality organic (indoor plant) fertilizer.

EDIT (additional information): Pine's like the weather to stay in between 50-70° F or (10-20 °C) and night time temperatures shouldn't drop below 40° F (4° C). If the species you have was harvested locally then it stands to reason that it could live outside on your terrace.