To be able to sign in to YouTube from these apps, you need the following versions:
- Final Cut Pro X 10.2.2 or later
- Motion 5.2.2 or later
- Compressor 4.2.1 or later
- iMovie for Mac 10.0.8 or later
- iMovie for iOS 2.1.2 or later
If you can't share your video to YouTube from one of these apps, check the Updates pane of the App Store on your Mac, iPhone, iPad, or iPod touch to see if an update is available.
If you're not able to update these apps, export your movie to iCloud Drive or a drive connected to your Mac. Then, use the upload tools on the YouTube website to upload your exported video to YouTube.