Check and make sure that the CloudPanel Service is running. This is what processes the email notifications and checks Active Directory for expiring passwords
Make sure that you entered an email template because if it is left blank then no emails will be sent.
Make sure that you actually enabled the notification under the Enable/Disable Notifications tab
Check the CloudPanel Service log file located in the log directory of the service. The job will be executed and contain a note when it starts: “Job Executed: Querying a list of users with passwords about to expire” and then when it is going to send the email it will state “Job Executed: Sending support notifications”