Steps to solve Outlook not authenticating correctly with Microsoft 365.

  1. Completely close Outlook application
  2. Clear the credential manager (remove anything related to the office 365 account)
  3. From the windows search bar type Access work or school and disconnect the account.
  4. Open the registry editor and navigate to the following location
    HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity:”EnableADAL”=dword:1 and type is Decimal 1
  5. Relaunch Outlook

Microsoft Office 2013 on Microsoft Windows computers supports Modern authentication. But, to turn it on, you need to configure the following registry keys:

Registry keyTypeValue

Hope this resolved it !!