This has been reported many times by only a small portion of users and cannot be reproduced for troubleshooting. As the error says, the server (Ford’s) is closing the connection.
This is what you could do:
- Keep trying until it succeeds
- Try a different computer
- Try a different network
- Configure Syn3Updater to only use a single download connection instead of 8
- Manually download the files via a browser and save them into the Syn3Updater download folder and re run the process: Syn3Updater will find the files locally and validate them without re-downloading and later create the USB drive.
EDIT BY CYANLABS: Use this link to get the files - Easily Update Your SYNC 3 Using Our Manual Method - CyanLabs