If you see customers present in the 'Owner Inbox Disconnected' bucket in the Data Sync tab, follow these steps to resolve.

If you've activated a Google or Microsoft domain install, the missing owner(s) should be added to the appropriate email list by your email IT admin (or anyone with access to manage that email list).

Send an invite to the owner from Staircase. They will receive an invitation to login to Staircase and from there will be prompted to grant permissions to sync email and calendar.