Note: You are currently viewing documentation for Moodle 3.3. Up-to-date documentation for the latest stable version of Moodle is probably available here: error/quiz/attemptalreadyclosed.


From MoodleDocs

This error message is obtained if you have a quiz open in two browser tabs, click 'Submit all and finish' in one tab, then attempt something in the other tab. You should have the quiz open in one browser tab only.