If you try adding your Office 365 or Microsoft 365 account to Outlook 2019, you may receive an error that reads Something went wrong. An example of this message is below:

Something Went Wrong when Adding O365 Account to Outlook

To solve this, you should check to see if Modern Authentication is enabled in your Office 365 Tenant. To do this, visit the O365 Admin Portal Settings and check the box to enable Modern Authentication.