When contact is defined in Scheduled offering details and an user is enrolled to the Scheduled offering then the contact does not receive the Contact does not receive SystemEnrollmentNotification.
Reproducing the Issue
If you are referring to contacts on offering details page, then that email address is meant for including the address info in notification to users as scheduled offering contact person email address and system will not generate any notification to that email address. System will generate emails to persons who are added as contacts in Scheduled Offering --> Related More --> Contacts and notify settings for Contacts is meant for these recipients only.
Make sure to maintain contacts in Scheduled Offering --> Related More --> Contacts.
Send notifications to Contacts is checked in the settings of scheduled offering.
Contacts in scheduled offering , KBA , LOD-SF-LMS-NOT , Notifications , How To