Hi @AudreyClements,
Could you explain a bit more about what you're doing? You mention deleting courses not in the selected file, but the error message you're mentioning is almost certainly in reference to an uploaded file. The error indicates that you're trying to do something with an enrollment where the section doesn't exist. Perhaps you're trying to delete both sections and enrollments in one upload? If so, that's not really necessary, you can just delete a course or section and that would take care of the enrollments too.
-Chris
