Why can't users see their alerts in the bell notifications?

If users' email alerts aren't appearing in the Notifications (bell notifications) list:

1. Sign in using a user role that has access to one of the workflow administrator roles. See Roles That Give Workflow Administrators Access for more information.
2. Click the Notifications icon in the global header.
3. Click Show All.
4. On the Notifications page, click the Worklist button.
5. In BPM Worklist, click your user name and select Administration.
6. On the Application Preferences page that's on the Administration tab, open the Test Notification Email Address field and set its value to a blank value (remove all the text inside it).