In case anyone else runs into this strange message when attempting to create issues from Confluence to Jira using "Create Jira Work Items" this is a bug.
The issue is not with workflow validators at all. You simply need to select "Configure", then change the field that maps to "Summary". Once the original "Table Column" mapping has been changed to something else, just change it back to what it originally was and select "Save".
Now the "Create all" button is enabled. No workflow or validators changes needed.