I use Turnitin with most of my assignments on Canvas and frequently have high plagiarism matches with submissions that are most likely from my own classes in prior semesters, but I can't access those older papers without requesting permission from the instructor (again, probably me). I've tried requesting permission but never heard anything. When I contacted Turnitin, here is what they wrote:
Canvas has created a plugin which allows Turnitin to integrate with the Canvas service.
The feature to allow "requests to view papers" is not currently supported by Canvas as the Canvas service does not provide Turnitin with a usable email address to contact instructors. Please contact Canvas for more information regarding this matter.
Turnitin is much more useful if we can use it to compare against our own students' papers from previous semesters. Are there any options to make this feature work?