When SSO Troubleshooting is enabled, the following error is seen:
The authentication mechanism is unknown.
SSO is configured to use LDAP Authentication. All information has been verified as correct in the SSO Configuration Tool. The "Test LDAP Authentication" button in the SSO Configuration Tool itself is always successful. However, when users attempt to log on via the web, they get the error "Unable to Authenticate User."
This will occur if the Application Pool for the SSO web service is not set to the Network Service user. Use the following procedure to resolve this: