It may take a while for user synchronization from Microsoft 365 tenant to backup portal at https://shield-cloud.nexetic.com/ to complete. Wait for a while, refresh the page and check again. You can also click ‘Refresh’ button (Sync Users with O365) at the left upper corner of Users page.
Once the user sync is completed, all domain users will be visible on Users page.
However, if complete list of domain users is not updated within a few hours, please contact our Support.