Business versus Personal Accounts at Microsoft
Microsoft operates separate user directories for personal (e.g. Xbox, etc.) and business accounts.
Prior to 2023, it was quite common to see the error below when trying to use a 365 Business account when logging in:
Microsoft will now typically re-direct you to the correct site automatically, but you may occassionally see the above error if you've clicked on a search result that only allows personal logins.
The simplest way to ensure you are logging into the business version of 365 is to click this URL.