After upgrading Splunk Enterprise Security from 3.0.1 to 4.0.1, why does the "Notable Events by Urgency" dashboard display "No results found"?

Hi all, Just upgraded Enterprise Security 3.0.1 to 4.0.1, all went well with the exception of one outstanding item. The **Notable Events by Urgency** dashboard listed under **Security Posture** remains unpopulated, listing *No results found*. I know there are notable events there, as the remaining dashboards populate, and all events are listed under the **Incident Review** section. Any suggestions as to where I should be looking to get this dashboard repopulated? I can't imagine it's a wait-to-fix scenario due to the upgrade as all the notable events are already there (and continuing to be created). Any tips much appreciated. Thanks, SB