If PBX users were added by anyone other than the Microsoft Global Admin, e.g., by your service provider, then you need to enable the services for those users on the Enterprise portal: go to Users and click Sync Teams Registrations.

If PBX users were added by anyone other than the Microsoft Global Admin, e.g., by your service provider, then you need to enable the services for those users on the Enterprise portal: go to Users and click Sync Teams Registrations.
