When exporting/importing a Microsoft SQL database or applying new backup settings for a remote MS SQL Servers at Tools & Settings > Database Servers > remote_MSSQL_ServerName > Backup section, the operation fails with the error message:
Unable to open network connection: A specified logon session does not exist. It may already have been terminated
(Error code 21)
Incorrect database user name specified in connection settings: the user on the remote server is set without network specification:
Go to Tools & Settings > Database Servers > remote_MSSQL_ServerName > Backup section.
Specify server name or IP address of the remote server with Microsoft SQL Server.
Click OK to apply the changes.