Microsoft Office Professional Plus 2016 and Windows 10 Pro on Surface Pro 3 connected to Exchange 2016:
When an email arrives that triggers an Action Item, clicking the add-in which says, "We think we've found an action item", causes the following error in the Action Items box: "The add-in wasn't loaded correctly. Please try again later."
The add-in is active both on the Outlook client and on the Exchange server.
The add-in functions correctly with a Microsoft Office Professional Plus 2013 Outlook client.
IT Specialist