Logging into Spotfire Cloud analyst happens through Web Authentication. As soon as the TIBCO Spotfire Cloud analyst is launched, it redirects you to the Web browser/internet browser and brings up a windows asking for credentials.

It is machines default browser that is launched. There have been few scenarios where the login does not work (in cases where the default browser is set to Microsoft Edge) and you may encounter the error below:
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Error message: Unknown Error

Win32Exception at System: The directory name is invalid (HRESULT: 80004005)

Stack Trace:
   at System.Diagnostics.Process.StartWithShellExecuteEx(ProcessStartInfo startInfo)
   at System.Diagnostics.Process.Start(ProcessStartInfo startInfo)
   at Spotfire.Dxp.Framework.Login.OAuth2AuthenticationFlow.OpenAuthorizationRequestInDefaultBrowser(String clientGeneratedCode, String redirectBaseUri, String clientGeneratedState)
   at Spotfire.Dxp.Framework.Login.OAuth2AuthenticationFlow.AuthenticateUsingBrowser(CancellationToken cancellationToken, String& authToken, String& refreshToken)
   at Spotfire.Dxp.Loader.LoginHandler.<>c__DisplayClass39_0.<ShowOAuth2Login>b__0()
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
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All supported operating systems

First thing to test here is to change the system default browser to some other browser like chrome, firefox and internet explorer. Then login should work.
Below are the steps to change the system default browser:
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Select the Start  button, and then type Default apps.
In the search results, select Default apps.
Under Web browser, select the browser currently listed, and then select another browser
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- The cause here maybe due to some windows updates which may have corrupted the MD EDGE browser. If you wish to keep MS EDGE as the default browser, try uninstalling and reinstalling it.

Unable to login to Spotfire Cloud analyst and the analyst gives error: Win32Exception at System: The directory name is invalid (HRESULT: 80004005)

https://support.microsoft.com/en-in/help/4028606/windows-10-change-your-default-browser

https://answers.microsoft.com/en-us/windows/forum/all/remove-twinui-from-default-apps/ae97c023-cbd3-48f4-8240-c90b0f1b918e