Affected user has the email address properly set on cmn_notif_device and sys_user tables

All logs show that the notification was sent to the right user

No delegates enabled for the affected user

No business rules affecting the sys_email or target tables

Notification preview shows the user in the recipient list

All

Notification device cmn_notif_device table has records with empty users

Notification is not mandatory but not necessarily subscribable

Delete the cmn_notif_device records with user field empty

Impersonate the affected user and make sure she is subscribed to the notification "Requested Item created Notification"

Additionally to previous step, it also works to enable the mandatory field in the notification to allow the affected user to always receive the notification

For more information about mandatory notifications, the official documentation portal has a page How to make mandatory notifications