You’re attempting to manage an SQL Server 2008 instance with Management Studio but are receiving an error 18456 when using AD authentication.
Error “Token-based server access validation failed with an infrastructure error” (event id 18456).
Follow these steps to debug the issue:
- First, make sure that you are logged in as a user with SA privileges. Management Studio will only use AD credentials of the current session; you cannot specify an AD user and password like you can for SQL Server Authentication
- Check the Application event log for the 18456 event:
If the error is “Token-based server access validation failed with an infrastructure error” the mostly likely culprit is UAC. Close Management Studio, right-click and select Run As Administrator. You’ll probably be able to login at that point.