Microsoft has confirmed that the issue is resolved. SharePoint Online and OneDrive for Business sync services are restored.

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Previous Description (May 1, 2019 17:34):

Users may be unable to sync recent Office document changes to OneDrive for Business and SharePoint Online Team sites.

This issue appears limited to the syncing of existing Office documents only and will only occur within the Office 2013 client or earlier versions.

Microsoft has begun deploying a fix for this issue and expects the process may require 24 – 48 hours to complete.

This notification will be updated when more information becomes available.