Enrolment

I'm using moodle 1.9.. I uploaded several students and enrolled them by myself (admin) to a course by linking them to the student-role. Normally this works fine, but now... First: the students cannot access the course, because they are refused. Second: neither coach or administrator can see enrolled students, it looks there is nobody enrolled. This is only the thing with students. Guests or teachers can be seen in f.e. the group building reens, students not. I made several courses that worked fine, now every course have the same problem: not possile to show enrolled students.