Symptoms

After upgrading to 4.6.11, when attempting to open a existing workflow in Visual Studio the following error is thrown:
Invalid archive type
 

Diagnoses

The "Invalid archive type" error usually indicates that the Client tool (K2 for Visual Studio) is likely not on the same version as the K2 server it is connecting to.

You can use the same installation files as the K2 Server to upgrade the client tools. It would detect that you only have the client tools installed and will only upgrade the client tool components previous installed.

You will likely need to run the 4.6.11 Setups on your client machine in the order below:
- K2 Blackpearl 4.6.11
- K2 Smartforms 4.6.11

The account running the upgrade/setup on you client tool machine will need access to the K2 database.
 

Resolution

Upgrading the client tools to the same version as the K2 server resolved the issue.