Symptoms

We had split single K2 site in IIS to Workspace and Smartforms sites and updated URLs. When we went through activating features via K2 for SharePoint app but previously site collections with K2 app enabled were not updated. These site collections were previously activated under unified K2 site url but I am now unable to activate these site collections again based on this KB article: https://help.k2.com/kb001753. The warning message mentions that the site should be first removed from the different K2 server, which we are unable to do because while it is the same environment, it was registered with the previous, unified URL. Is there an alternative method to remove or re-register the K2 for SharePoint app on these sites with the new K2 URL?
 

Diagnoses

Default SmartForms_Runtime_URL value was still pointing to old K2 site url in K2 hidden list
on previous activated site collection (?/sites/site_collection_name/Lists/K2 Settings/AllItems.aspx)
 

Resolution

Updating the Smartforms_Runtime_URL to the new url resolved the issue.