Since the 1/16/20 Update, clicking on the Add button on the View MST pop-up on the Classes page is not always properly adding sections to student's schedules. Programming is investigating the issue and a fix will be released soon.
Until the fix is released, please use the other methods on the Classes page for adding sections: adding courses to the Course/Current Class field and selecting a section, or typing in a section number to the New Class section number pop-up field. Alternatively, the Classes Old page may be used.
Has there been any progress on this issue?
Yes, the fix for this issue has been programmed and will be released as soon as it passes QC.