Check these things.

  1. On the notification, verify the notification table is correct.

  2. On the notification, verify the conditions are met.
    KB0528655

  3. On the notification, verify the "Send to event creator" is correct. This doesn't care how the event creator is included if scripted, parm1 or 2 it will include if checked and exclude if unchecked.

  4. On the notification, verify the "Send To" or "Send to Event Parm1"
    or "Send to Event Parm2".

  5. On the notification, verify there is something in the Body of the
    notification.

  6. On the notification, verify the weight is set. If it's not zero,
    check the skipped folder. Weight

  7. On the user, verify they are not locked out.
    KB0528699

  8. On the user, verify they have an email, and it's properly formed.
    KB0528671

  9. On the user, verify they have an email account, is active, has no
    notification issues

  10. On the user's notification devices (cmn_notif_device_list.do),
    verify the user has a "Primary Email" device and it it correct.
    KB0528667

  11. On the user's notification subscriptions, verify they haven't
    disabled this notification.
    KB0516987

  12. If event generated

    • Verify the event exists on
      sysevent_list.do?sysparm_query=sys_id=-1.
      KB0523579
    • Check the Event record table is table is correct.
    • Verify the Events Process job is running
      KB0523580
      Youtube
  13. Validate any mail is working

  14. Validate the system is not sending to the debug user. Outbound Mail Configuration

  15. Validate the system is enabled to send email
    KB0524529

Thanks Andrew Barnes and some other random person from sndevs.slack.com
for the inspiration to make this post.

Weight

Set a numerical value for the notification priority relative to other
notifications with the same target table and recipients. The system
only sends the notification with the highest weight. All other
notifications are moved from the Outbox to the Skipped mailbox. The
default value 0 causes the system to always send the notification
(assuming the conditions are met).

For example, suppose that a service desk agent adds a comment to an
incident and shortly thereafter closes it. By default, these actions
trigger both the Incident commented and Incident Closed notifications.

However, both notifications are from the Incident table and also
notify the incident caller. The system only sends the notification
with the highest weight, which in this case is the Incident Closed
notification.

Determine whether any of the troubleshooting steps below are true for
your environment. Each step provides a link to an article that will
help you eliminate possible causes and take corrective action as
necessary.

This is from the
docs.