That error message means that CData Sync is unable to write to its internal application database to save the new connection. Here are some of the potential causes of this error message:

• Usually, this is a permissions issue. Double-check the file and directory permissions for the Sync installation folder, as well as the Sync application directory (specified in the Web.Config file)
• If you are running Sync as a desktop application in the system tray, you may also be able to eliminate this issue by running Sync as an administrator.
• Less commonly, this error could occur because there is no free storage space, preventing Sync from writing changes to its application database (for example, this could happen if you are running Sync on a VM with limited storage space, and the drive inadvertently becomes filled with log files). Check the available storage on the machine running Sync.