I allowed three students to submit their papers late. They did so and I can view their submissions on Turnitin and on the Assignment page, but their submissions do not show up in Grade Book or in the Speed Grader.
I found an article from FSU's Canvas Support Center describing a known issue with TurnItIn not adding submissions to speedgrader or the gradebook because of students leaving the submission portal open too long before submitting their assignment: Known Issue: Turnitin Submission not appearing in SpeedGrader or Gradebook - FSU Canvas Support Center
Their only solution is to have the student resubmit the assignment.
Since it has only happened to three students, you could just download their submissions from TurnItIn, make any corrections in MS Word, email it back to them and then input the grade manually in the gradebook.
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