There is a truly bizarre and unfortunate default in moodle quizzes, which is that if the time runs out on the quiz without a student having submitted the quiz, it is not submitted for them, is not marked, and can never be retrieved (though what they have done is saved and can be seen.)
Fortunately, there is an obscure option that can do the sensible thing and submit the quiz for them when the time runs out. But you have to search to find this.
If you didn't find that option, or forgot one time to set it, and now you are trying to get your quiz properly marked, you may eventually find the relevant Moodle Quiz FAQ which admits there is no way to retrieve the quiz and suggests "Perhaps the best solution is to plan ahead and set your quiz to set your quiz to be submitted automatically." Why yes, what a brilliant plan! I do indeed now waste a lot of time finding that option every time I make a quiz. Perhaps the best solution would be for the moodle developers to plan ahead and get rid of this default? I can't imagine why anyone would want their students to fail because they were concentrating on the quiz when it ended!
How hard can fixing this possibly be? I have found it as a "known issue" with a tracking number in an older FAQ that unlike the one I links says it will be repaired. Has moodle decided to keep this "feature"? Why can't I just reset the end of the quiz to today, reset the option to submit on completion, and retrieve the students performance that way? Or better yet, why can't we just select the attempts and push "regrade the selected attempts", and if necessary click something confirming that we are submitting on the student's behalf? Why do I need to try to haul students in to click buttons for me?
I should say that otherwise the quiz programming is outstanding; I've been really impressed. But this issue obviously has me completely flummoxed, and my marks are overdue. I never believed it could be this hard to find a solution.