Once a user has been deleted in Microsoft365 Administrative Console, they will only be set to disabled in the Business Central system when the next sync is run. To delete the user complete the following steps:
  1. Open the User Settings List.
  2. Delete any User Settings for the userid that is to be removed.
  3. Once all entries are deleted, open the Users List.
  4. Select the user, then go to the Manage menu, then click Delete. Answer yes to the pop-ups.

Once done, if no errors occur the user should no longer appear in the Users List.