I did a test, @CraigDay and it worked as advertised for me. Here is what I have for the relevant quiz settings:
Quiz response options
This quiz allows unlimited attempts, and student users are able to see the correct answers only once, when they submit the quiz. After that, this is what a student user sees when they return to the quiz page:
Student user view of quiz
If your students' users are encountering something different, the best option is to use the Help menu in your Canvas instance to alert your tech support team. It would be great if their vigilance extended to the Canvas Question Forum, alas it does not.
I’m going to mark this reply as a solution. I realize it does not solve your problem, but it might help colleagues who face a similar challenge.