Work with your local IT department to resolve connectivity issue.
Cause
Typically this error occurs when the proxy server does not allow host names/FQDN to pass through; and this blocks communication with Tableau Server.
Additional Information
While this error looks like a Tableau Server error, it was actually a proxy error sent in HTML from the proxy server. Tableau Server wraps the HTML in a 'Tableau Exception' because the error cannot be interpreted.
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