I'd suggest performing a network trace between the PC/Mac where this error happened to the web server then trace back to Tableau Server. Something is not setup properly.
I would need a lot more details and cannot diagnose network issues remotely. I suggest working with Tableau Services where they can come out and configure the servers for you. Suggest reaching out to your Tableau Sales Rep for advice and help with getting services to assist.
Hi Jilani -
You can do a quick test by pinging the server to see if you can reach it.
ping server-name or IP address
I agree. I sure hope that a proper DNS Hostname is assigned to Tableau Server and that they are not using an IP address to reach the server. That's ok in a test situation but not for production.