I made a new quiz, posted it, and had 2 classes take it on one day. I was able to grade them in speed grader and everything went fine. Then, the next day I had kids from the next classes take it and when I try to grade it or access it in any way from Canvas (through quizzes, modules, speed grader, etc.) I keep getting kicked back to the home screen and get the error "Couldn't find valid settings or this link". I didn't change anything about the quiz and now I can't grade two periods of quizzes because I can't get into the quiz.
Also, I just checked and ALL my quizzes I have build are giving this error, published and unpublished, taken or not.
So I think I have figured it out from some other research in the community. Over the weekend, our school district changed the external tool link for our new quizzes from "ccsd.instructure.com" to "hsccsd.instructure.com" which basically "broke" the link and makes it not work. Teachers in our district don't have access to manually change the link (I'm convinced if they just add the hs to the front, it will work), so I have admin looking into if they have access to just change that link and see if it works and recovers the quiz.
@MsW We're in the process of reviewing some of our older questions and came across this one. Was your hypothesis about the changed external tool link correct, and was the district able to straighten this out for you and your students?