After installing the May 2017 Cumulative update and navigating to the K2 application on a SharePoint list, you will notice that it does not list the existing SmartObjects, but instead wants to create new SmartObjects or deploy a package.
Existing SmartObjects are not listed from the K2 application on a SharePoint list.
As per the K2 compatibility matrix an SQL upgrade would be neccessary to place your system back into a supported state as SQL 2008 and K2 4.7 will leave your environment in an unsupported state. An SQL upgrade would be required which supports K2 4.7. K2 blackpearl and K2 smartforms: Product Compatibility, Integration and Support