"A certification authority could not be contacted for authentication.
If you are using a Remote Desktop Gateway with a smart card, try connecting to the remote computer using a password.
For assistance, contact your administrator or technical support"
This can occur if you have performed an authoritative restoration on the Users container in the Active Directory directory service. When this is done the version number of the KRBTGT account increases which is a service account that is used by the Kerberos Key Distribution Center (KDC) service.
Resolution:
This is essentially the same issue as the one documented in the following Knowledge Base article:
KB939820 - Events 1925, 1006, 1645, 1055, 40961 on a Windows Server 2008-based domain controller or error message: "No authority could be contacted for authentication" when you use Remote Desktop Connection
To resolve the issue apply the hotfix specified in the Knowledge Base article above. Note that you must restart the computer after you apply this hotfix.
Satish Phatge | System Center Support Engineer
