This issue appears after upgrading the Dev environment from Visual Studio 2012 to VS 2015. There are several K2 workflows supplementing the .NET application. When attempting to open the K2 Solution in VS 2015, an error appears.
When both K2 components: ‘K2 for Visual Studio 2012’ and ‘K2 for Visual Studio 2015’ installed, K2 solutions built on K2 for Visual Studio 2012 with workflows supplementing the .NET application, fails to open.
To resolve this issue, follow the steps below to remove the K2 Client Components (K2 for Visual Studio 2012).
1. Launch K2 Setup Manager from the K2 Installer
2. Select modify and click next
3. Uncheck the K2 Client Component ‘K2 for Visual Studio 2012’
4. Click next until the K2 Setup Manager finishes
5. Try to open your K2 Solution which should open without the error appearing.