"email@example.com" and "firstname.lastname@example.org" are Office 365 accounts .
My PC and user's PC are Windows 10 , with Office 2016 standard
I can add "email@example.com" to MS Outlook on my pc and user's pc
I can't add "firstname.lastname@example.org" to MS Outlook on my pc and user's pc but I can access it from the web.
I go to https://testconnectivity.microsoft.com --> Office 365 --> Outlook Connectivity and test "email@example.com" with Modern Authentication (OAuth) credentials successfully.
How can I troubleshoot it ?