Pending Payment defult message is not working since years an i just noticed that. i filtered the sent messages for “pending payment” status and as you can see its not sending since 2017 https://i.imgur.com/TCix6Ft.png
It could be the individual messages templates are not activated. You can check those by going to Event Espresso > Messages > Default Message Templates. Then go in and edit each of the contexts (Edit Event Admin, Edit Primary Registrant) for Registration Pending Payment message type. There’s a gray/green toggle switch for each template. If it’s gray, that means it’s deactivated. If the toggle is green the template is activated.
Also, you’ll check the “To:” field for each template. If the “To:” field is empty or doesn’t have an email address or a shortcode that parses an email address, then the email will not send.