Students cannot access quizzes attached to a course module

Students get a "No permissions to view quizzes" message at the end of a module when they attempt to take the quiz. Interestingly if a quiz is not attached to a module they still get the same message.

There is nothing in Drupal logs to show access was denied, it seems to be handled from within Anu LMS. I've tried it with a fresh course, fresh lesson, and fresh quiz, same result.

Baffled.