A voice call to user %1 failed because it is not possible to determine the user's Unified Communications (UC) policy. It ...

A voice call to user %1 failed because it is not possible to determine the user's Unified Communications (UC) policy. It is likely this problem affects other users as well. Problems with this user's policy will not be reported again for another hour.
Cause: Active Directory settings may have become corrupt.
Resolution:
Verify that the voice policy is correct or assign valid voice policy to users.