When publishing a connection to Tableau Server the following errors might occur:
SQL Server database error 0x80004005: Login timeout expired
SQL Server database error 0x80004005: A network-related or instance-specific error has occurred while establishing a connection to SQL Server. Server is not found or not accessible. Check if instance name is correct and if SQL Server is configured to allow remote connections. For more information see SQL Server Books Online.
SQL Server database error 0x80004005: Named Pipes Provider: Could not open a connection to SQL Server .