This can be due to the begin date listed for the student in that course in their enrollment.
As a Schedule Manager:
  1. Navigate to Academics.
  2. Select People Finder > search/select a student from the course, that is missing from Take Attendance.
  3. Click the Enrollment tab.
  4. Check the Begin Date listed for the course. This must be current for the student to show in attendance. If this is in the future, you can drop the student, then re-enroll with the correct date.
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