"The request failed with HTTP status 401: Unauthorized" error when connecting to Sharepoint. (4278922)

"The request failed with HTTP status 401: Unauthorized" error when connecting to Sharepoint. 

• MEWS and Windows Authentication

• Auto Authentication 

The "401 Unauthorized" error can be caused by the following:

• There may be insufficient permissions in web application user policy for the connecting user account.
• More than one authentication providers are configured on the Web Application in SharePoint.
• Connections switching between WFE servers due to session affinity (sticky sessions) settings of the Network Load Balancer.
• There may be a mismatch in anonymous access settings in IIS Manager vs SharePoint Web Application.
• The SharePoint web application uses “NTLM” authentication instead of Kerberos authentication and has anonymous access enabled in IIS Manager. 

Workaround

1. Grant direct explicit (Not through a group but through an individual account) full control permissions through Web Application user policy to the connecting user account (For example Quest\Peter).
2. If step 1 doesn't work, try connect at Farm level using a Farm Admin account. Next drill down and see if SharePoint can connect Or still get the 401 Unauthorized error. 
3. Connect directly to SharePoint Web Server by configuring a host file entry on the machine running Content Matrix to bypass the Network Load Balancer.
4. Consider disabling the Anonymous access in IIS manager if anonymous access setting is not enabled on the affected Web Application in SharePoint.
5. If the above steps did not work, implement Negotiate (Kerberos) authentication on the affected SharePoint Web Application, refer to here.