Error Message: A student must be taking at least 1 class, but no class records could be found for this student.
The problem is that on “Schedule > Courses”, none of the courses have a Data Rollup Subject selected.
So go to “Schedule > Courses”, and click on each course, one at a time. Then, at the top right, make a selection from the “Subject” menu. When you are done, you can resubmit to Data Rollup, or wait for tonight’s export.