Registration Confirmation email

We used to receive emails when a participant submitted a registration request, and suddenly we no longer receive a notification.  I have checked the Outlook folders for the emails, and found nothing even in the  SPAM folder.  I then checked in our mail quarantine and there weren't any registration emails in that folder from registrants.

Please let me know if there is something else that I can check or change to enable to receive the registration emails again. I already checked if the registration confirmation mail is enabled, I even unchecked it and then rechecked it to see if it works.