Late last year, some updates were made to the Canvas plagiarism framework integration to allow for assignments to be copied regardless of what dates were passed to Turnitin, as well as allow support for anonymous grading in Canvas.
If Turnitin received an assignment start date too far in the past or too far in the future, we would ignore this date and create default dates in the future to allow for the assignment to still be created in Turnitin.
Although we have fixed these particular issues, we no longer apply the due date correctly within Turnitin, and all dates now default to a point in the future. Unfortunately, this affects when collusion checking occurs. We are currently investigating a fix to allow the due date to update correctly if the user in Canvas provides a suitable date, and we plan to release a fix alongside the fix for updating the Similarity Score in Canvas.
Fixed date - March 12th 2019