Unable to login to TIBCO Spotfire Analyst with the error "The remote server returned an error: (401) Unauthorized"

Unable to login to TIBCO Spotfire Analyst with the error "The remote server returned an error: (401) Unauthorized"

When trying to login to the TIBCO Spotfire Analyst client it fails with the following error:

Error message: An unknown error has occurred.

UserDirectoryServiceException at Spotfire.Dxp.Services:
The server could not be reached (HRESULT: 80131509)

Stack Trace:
   at Spotfire.Dxp.Services.WebServiceBase`1.InvokeService[T](ServiceMethod`1 serviceMethod, ExceptionFactoryMethod exceptionFactoryMethod)
   at Spotfire.Dxp.Services.UserDirectory.UserDirectoryService.GetPrincipal(String guid)
   at Spotfire.Dxp.Services.Authenticator.Authenticate(SpotfireIdentity identity, PrincipalProvider provider)
   at Spotfire.Dxp.Loader.LoginHandler.PerformLogin()

WebException at Spotfire.Dxp.Framework:
The remote server returned an error: (401) Unauthorized . (HRESULT: 80131509)

Stack Trace:
   at Spotfire.Dxp.Framework.HttpClient.NativeWebResponse..ctor(NativeHttpClient httpClient, NativeWebRequest request)
   at Spotfire.Dxp.Framework.HttpClient.WinINet.WinINetWebRequest.GetResponseCore()
   at Spotfire.Dxp.Framework.HttpClient.NativeWebRequest.GetResponse()
   at Spotfire.Dxp.Services.SessionEnabledSoapClient.GetWebResponse(WebRequest request)
   at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
   at Spotfire.Dxp.WebServices.UserDirectoryService.getPrincipal(String id)
   at Spotfire.Dxp.Services.WebServiceBase`1.InvokeService[T](ServiceMethod`1 serviceMethod, ExceptionFactoryMethod exceptionFactoryMethod)

If you try to open the same TIBCO Spotfire Server URL in Internet Explorer it may fail with an error like:

This site uses JavaScript. Your browser does not support JavaScript

This authentication error can be seen if the TIBCO Spotfire Server URL is not in the list of Trusted Sites in the local client machine's Internet Options, which will restrict the functionality of the site and may interfere with Spotfire authentication.
  To resolve, add the TIBCO Spotfire Server URL to the Trusted Sites internet zone in the local client machine's Internet Options:

1. In Internet Explorer, click "Tools" icon and select "Internet Options".
2. In the "Internet Options" window select the "Security" tab.
3. On the "Security" tab select 'Trusted sites' and click on 'Sites'
4. Add the TIBCO Spotfire Server URL and click on 'Close'
5. In the "Internet Options" window click on the "OK" button to close it.

Now try and log in with the TIBCO Spotfire Analyst client again. 

Note: The test login using the browser failed with the JavaScript error due to Internet Options site restrictions. To get the web authentication to work, enable "Active Scripting" for the zone the TIBCO Spotfire Server URL is in. To update, perform these additional steps between steps 4 and 5 above:

• On the "Security" tab click on the "Custom level..." button.
• When the "Security Settings - Trusted Sites Zone" dialog window opens, look for the "Scripting" section.
• In the "Active Scripting" item select "Enable".
• When the "Warning!" window pops out asking "Are you sure you want to change the settings for this zone?" select "Yes".

Doc: How to enable JavaScript in your browser

• https://www.enable-javascript.com/