I'll second Helen's #1: If the participant does not have Student role in the class, they won't see some types of activity. It could be they have guest access or it could be you gave them category level student roles (which don't work like enrollment, so don't! This way leads to madness!).
If you want to 'enroll' a big group of people into a bunch of courses, create a cohort and then enroll the cohort in each course.