Please have a look at this KB article relating to the same type of issue you are having.
Please let me know if this helps.
The best idea that I have is:
In K2 Management, go to service instances and check if K2 Workspace is there:
If it is not, then press the add button at the top panel, select the K2 Workspace service type and name it K2 Workspace.
The settings hsould autot generate, yu just need to click the generate SMO checkbox:
If K2 Workspace is already in your service instance, then i recommend opening a support ticket. You can also perhaps click the generate SMO checkbox in hopes that it will reconfigure the smart objects for workspace, but im not sure if it will delete any existing data.
Apologies that you have to deal with this issue :(