The default "Email From" type when you create an Official Note is Review Comments. If the Official Note does not require approval, you need to change "Email From" to Comment or the notification will not send.

In onRecord:
  1. Select Settings > Comments
  2. Select Comment Types
  3. Edit the Official Note type
  4. In the "Email From" field, mark the radio button to the right of Comment
  5. Click Save & Exit