In Pronamic Pay version 8 we have removed support for s2Member. Due to the complexity of the s2Member plugin we have decided to no longer support the s2Member plugin. The integration has therefore been permanently removed in Pronamic Pay version 8. If you still use s2Member, now is the time to switch to MemberPress, Restrict Content Pro or Gravity Forms.
.src/includes/classes/email-configs.inc.php#L291-L346