In K2 Designer, when trying to configure "Start with a SharePoint List", the following error may occur:
Before You Begin
The error could be caused by an unsupported SharePoint list in the Site Collection. In this example, the SharePoint custom list does not have the required OOB “Item” Content Type.
To resolve this, add the “Item” Content type in the problem list. This allows K2 Designer to discover all the SharePoint Lists in the Site Collection successfully.