The error “Cannot trust the server to establish a SSL connection” means that you have enabled SSL in the VDP Server, but haven’t imported the certificate file(public key) into the truststore of the external client, in your case, Tableau.
I believe the steps mentioned below would help in rectifying the error:
* Make sure SSL is enabled for external clients by setting the property ‘javax.net.ssl.trustStore’ to point to the truststore of the Denodo server. For detailed information, You may refer to [Enabling SSL/TLS for External Clients](https://community.denodo.com/docs/html/browse/7.0/platform/installation/postinstallation_tasks/enable_ssl_connections_in_the_denodo_platform_servers/enabling_ssl_for_external_clients) under the Post-installation tasks section of the Denodo Platform Installation Guide.
* You have to import the public key file into the truststore of the external client(Talend). For detailed information, You may refer to [Obtaining and Installing an SSL/TLS Certificate](https://community.denodo.com/docs/html/browse/7.0/platform/installation/postinstallation_tasks/enable_ssl_connections_in_the_denodo_platform_servers/obtaining_and_installing_an_ssl_certificate) under the Post-installation tasks section of the Denodo Platform Installation Guide.
Hope this helps!