We have swapped out the default SSRS2012 Windows Authentication with our own FormsAuth custom authentication.

From SSMS2012, I can connect to our reporting server instance via FormsAuth without issue.

From SSM2014, I can't connect to our reporting server instance.  I get this error:

Invalid namespace (Microsoft.SqlServer.Management.UI.RSClient).

How should I troubleshoot / resolve this error?

Hi scott_m,

Based on my understanding, you come across an Invalid namespace error when connecting to Report Server from SSMS 2014.

In your scenario, are you connecting to a named instance? If that is a case, please make sure the Server name is correct when you connect to Report Server via SSMS. It should be <server name>\<instance name>. The following thread is about similar issue, please refer to:

Cannot connect to Reporting Services

If you have any question, please feel free to ask.

Best regards,
Qiuyun Yu