I am using version 3.5.2, and establishing group and Group Enrollment Keys. However, this version is not asking for the GEK during email enrollment and the students land in one big universal group. I have used previous versions of Moodle for about 6 years. How do I configure this version?
Did you set an enrolment key for the course as well (and made sure to ONLY tell the students their group enrolment key)?