When you use Database Engine Tuning Advisor to tune a database that uses a supplementary character collation in an instance of Microsoft SQL Server 2014, you receive the following error message:
Cannot successfully retrieve recommendations information.
Invalid session id (DTAClient)
Cumulative update information
The issue was first fixed in the following cumulative update of SQL Server 2014:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. We recommend that you download and install the latest cumulative updates for SQL Server 2014:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.