This error means your version of the Team Foundation Server client that SQL Source Control is using is incompatible with your version of Team Foundation Server (TFS).

See Team Foundation Server version compatibility for more details.

How to change the version of Team Explorer that SQL Source Control uses

You can change the version of Team Explorer that SQL Source Control uses by modifying a config file:

1. Make sure you've installed a version of Team Explorer that's compatible with your version of TFS.
   

   You don't need to uninstall any later incompatible versions.

2. Make sure Management Studio is closed.
3. Go to the SQL Source Control config files folder: %localappdata%\Red Gate\SQL Source Control 6

4. Open RedGate_SQLSourceControl_Engine_EngineOptions.xml in a text editor.

5. Inside the EngineOptions version tags, add:
   <TeamFoundationServerDllOverride>TFSxxxx</TeamFoundationServerDllOverride>
xxxx is the version of Team Explorer you want SQL Source Control to use.  

   Example

   <EngineOptions version="3" type="EngineOptions">
   	<TeamFoundationServerDllOverride>TFS2010</TeamFoundationServerDllOverride>
   </EngineOptions>

6. Save the file.

How to connect without using Team Explorer

Introduced in SQL Source Control 4.1.13, the TFS Extended Client allows SQL Source Control to connect to Team Foundation Server without using a Team Explorer client.

This also provides support for TFS 2015. To use this client:

1. Make sure Management Studio is closed.
2. Go to the SQL Source Control config files folder: %localappdata%\Red Gate\SQL Source Control 6

3. Open RedGate_SQLSourceControl_Engine_EngineOptions.xml in a text editor.

4. Inside the EngineOptions version tags, add:
   <TeamFoundationServerDllOverride>TfsExtendedClient</TeamFoundationServerDllOverride>


   Example

   <EngineOptions version="3" type="EngineOptions">
   	<TeamFoundationServerDllOverride>TfsExtendedClient</TeamFoundationServerDllOverride>
   </EngineOptions>

5. Save the file.