Symptoms

In the K2 application Server in the Event log we see this error:

"10702 Retrying the SharePointIntegration Service Instance as the K2 Service Account did not resolve the issue. Root element is missing."

And Groups Update doesn`t works for one of SharePoint Sites.
 

Diagnoses

The user had recently added an alias to their SharePoint site. Since the K2 app had been registered before the alias was set up, the K2 connection broke.
 

Resolution

Removing the app from the site in question and re-adding it resolved the issue.