There are several possibilities as to the reason why this error occurred. First, check if the Virtual DataPort server is on. You can check with the Denodo Platform Control Center or ping script in
'<DENODO_HOME>/bin'. You can refer to [Using the Ping Script](https://community.denodo.com/docs/html/browse/8.0/en/vdp/administration/cluster_architectures_server_backup/how_to_check_if_a_virtual_dataport_server_is_alive/how_to_check_if_a_virtual_dataport_server_is_alive#using-the-ping-script) in the **Virtual DataPort Administration Guide** for more information.
If the Virtual DataPort is running and you are still not able to connect, there may be an issue with the port you are using. With Tableau version 2021.4, you can use the JDBC driver to connect to Denodo. The default port for JDBC is 9999. If you are using an older version of Tableau, then you need to use the ODBC driver to connect to Tableau. The default port for ODBC is 9996.
If there are still issues connecting to Tableau, then verify that your credentials are correct to connect to Denodo. You can refer to the [How to Connect to Denodo from Tableau Desktop](https://community.denodo.com/kb/en/view/document/How%20to%20connect%20to%20Denodo%20from%20Tableau%20Desktop) article in the **Knowledge Base** for more information.
Hope this helps!