Why is my FaceTime not working in Taiwan, and how can I fix it?

My Facetime suddenly stopped working. I am Taiwanese and I have reported the problem to the Taiwanese customer service for more than 2 weeks. It has not been resolved yet. The Taiwanese customer service staff also don’t know the reason. Is it because the Taiwanese technical staff will not handle it? Doesn’t the head office manage it?

[Re-Titled by Moderator]