Lost access to shared dashboard

I have a customer who created several group workspaces and shared them with individual people.  Later on, he deleted the groups that were created in Active Directory.  Now, the person who created the group workspaces can no longer see them on PowerBI.com.  The individuals with whom the dashboards were shared are still able to see the dashboards and the refresh is operational, but the original owner no longer can see nor access the group workspaces.  How can I figure out who (if anyone) owns the group workspaces?