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Also, I just checked and ALL my quizzes I have build are giving this error, published and unpublished, taken or not.