When a student test is submitted, the accompanying information (metadata) surrounding the tests is checked for validity. This metadata includes information such as organization, enrollment, and student record. If any of these or other configured metadata validation tests fail, the student test will be rejected. The details of why the test was rejected are stored in the system so that they can be read by a human and corrected.
To learn why a student test was rejected, view the metadata, and fix errors, follow the steps on this page: