Sites do not load: HTTP Error 401.2 - Unauthorized

Symptoms

Websites fail to load with the following error:

HTTP Error 401.2 - Unauthorized 
You are not authorized to view this page due to invalid authentication headers.
Module
UrlAuthorizationModule
Notification
AuthorizeRequest
Handler
ExtensionlessUrlHandler-Integrated-4.0
Error Code
0x80070005

Cause

URL Authorization is enabled in Add Features and Roles Wizard > Web Server (IIS) > Security .

By default, there are no rules installed for this module in IIS Manager > Server > Authorization Rules that cause such an error.

Resolution

• Connect to the server using RDP .
• Remove module URL Authorization from Add Features and Roles Wizard > Web Server (IIS) > Security. Reboot the server.

OR

• Open IIS Manager > Server > Authorization Rules and add a rule Allow for All users .