Users will receive an error ‘HTTP 500 Internal Server Error’ while trying to browse to a SharePoint site using Claims-based authentication.
The following error message under the event viewer on the SharePoint server
Log Name : Application
Source : Microsoft-SharePoint Products-SharePoint Foundation
Date : <Date and Time>
Event ID : 8305
Task Category : Claims Authentication
Level : Error
User : domain name\username
Computer : servername
An exception occurred when trying to establish endpoint for context: An error occurred loading a configuration file: Either a required impersonation level was not provided, or the provided impersonation level is invalid.
The Application pool account was missing the “Impersonate a client after authentication” user right.
We can resolve this issue by following this
3. Reboot the server, so the changes can take effect
4. Browse the site and it should work fine.