@toms I was doing a bunch of testing on this last week and everything did work. As @Ron_Bowman stated, the "due" and "until" times serve very different purposes. Due, is when students need to have it done, and Until is the last opportunity they have to work on it, the "hard cutoff" (which may involve a penalty).
In new quizzes and classic quizzes all of this MUST be done before a student starts the exam. There is some misleading information in the community that you can change it once a student has started but this will not work. So your attempts to change it once the student was in, would not have worked. I believe this is because letting an instructor change the time once a student was in, could also work against them (like changing an extension of 90 min to 60). That is just a guess though.
For the setup, New Quizzes looks at the until time, the moderate/accommodations, and when the student beings the quiz and does all the math. For example, if I have given students 90 min to take an exam and set the until time for 3pm and a student starts taking it at 2pm, the clock will only show (and the quiz will only allow) 60 min for the exam. The until time completely overrides the allowed quiz time both for all students and any accommodated ones. It sounds like you did account for that in your setup but just including it here.
As a side note, you can't make an Until time before the Due date, Canvas will bark at you.
If you feel like you did all of this and made the changes before the student(s) started, I would reach out to either your school's Canvas admin or Canvas support and have them take a look. From all the testing I have been doing, it should have worked.
Not sure any of that helped but thought I would share.
-Nick
This discussion post is outdated and has been archived. Please use the Community question forums and official documentation for the most current and accurate information.