Hi @bluedogranch. Unfortunately, the MailPoet cron can only be accessed from your server’s command line and won’t work from external services.
In MailPoet > Settings > Advanced > Newsletter task scheduler (cron), when you select Linux cron, there is a command that is used, which already include the argument that’s needed for it to function (the argument includes a path to your WordPress installation on your server). You can’t pass this argument from an external cron service.