As you know, the sharing feature is based on the third party websites such as yotube, facebook, vimeo etc., our software just reference third party website APIs to do this, so this issue is not caused by our software directly.
Sometimes due to the third party websites update, it may cause this issue. Usually after finishing update, it will be fine. We'd suggest you try it in 1~2 days later.
Or you can try another way to export a video to your local computer first and then share the video from your computer.
Here is an example on how to save to a local computer and then share to youtube:
1. Click export and choose to export to a standard video such as mp4 to your computer.
2. Sign in Youtbue and then click upload and choose the video from your computer to upload.