The error details are minimal so I am not sure what could be the actual cause of the issue you are facing but I would recommend the following steps for troubleshooting:
* If you are connecting through a load balancer then try to connect to VDP server directly and bypass the load balancer.
* Try to check if the VDP server is running using the Ping script. Refer this documentation for the [Ping Script](https://community.denodo.com/docs/html/browse/7.0/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).
* If there is a firewall then make sure that it is turned off for testing purposes.
* Make sure that the required ports are open. The default ports used by the Virtual DataPort server can be found in the [knowledge base article for Ports needed by VDP server](https://community.denodo.com/kb/view/document/Ports%20needed%20by%20the%20VDP%20Server?category=Operation)
For further details on the issue, refer to the vdp.log file.
Hope this helps!