My students are unable to submit their assignments on either the app or browser currently. Has something changed from last week?
Canvas did have an issue taking place at about the time you submitted this question. I've posted a link below to the specifics, but from the title it sounds like this could have been the issue (Assignments and quizzes showing error messages). The issue was resolved on the 27th at 10:46 am mountain time.
Canvas Status - Assignments and quizzes showing error messages
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