For security reasons, we don't allow Email Automation messages to be sent to contacts created BEFORE the auto-message was created.
We added this automated-security-condition as we don't want our customers to mistype an auto-message condition that matches all previously-created contacts and spam them with the email they just set up.
That's why Email Automation messages are triggered ONLY for contacts created AFTER this auto-message is created.
For example, If a Contact that matches all of my auto-message conditions was created on 2019-08-15 07:49:36, and my auto-message was created on 2019-08-16 11:03:09. My contact wouldn't receive it.
If you think your undelivered messages are due to something else, feel free to live chat with us!