Sometimes when using Turnitin for an assignment it will show that the student does not have anything submitted in the speed grader portion of Canvas,  However when you check Turnitin, they do have it submitted.

Known Issue: Turnitin LTI Submission not appearing in SpeedGrader There is a known issue with Turnitin submissions not appearing in the Canvas SpeedGrader or Gradebook and only appearing in Turnitin’s Assignment Inbox. This is likely due to the student leaving the assignment’s submission portal open on their web browser for an extended period of time before submitting the assignment. To prevent this error from occurring, we recommend that students have a secure internet connection and not leave the submission portal open for longer than necessary.

Explanation and Solution: If a student leaves the Turnitin submission portal (iFrame) open for a long duration of time on their web browser, it is possible that when they submit their assignment to Turnitin it will not appear in the SpeedGrader or Gradebook in your Canvas course. It will be visible only through Turnitin’s Assignment Inbox, but will show as “No Submission” in the Gradebook and SpeedGrader. Currently, the only known solution provided to us by Turnitin is to have the student resubmit the assignment through the assignment portal in Canvas.