Course activities copied from an older Moodle version to Moodle 3.2 need to have the Turnitin settings reapplied to have them work correctly with Turnitin.
For example, if you had a course in an older Moodle version that had activities (assignment, forum or workshop) using Turnitin, when that course is copied over to a newer version of Moodle, you will have to re-enable Turnitin for those activities in the new course.
Re-enabling Turnitin on copied course activities
Go to the course site that has the copied activities.
Click the Turn editing on button.
Find the link to the activity (assignment, forum, or workshop) you want use with Turnitin.
Click the Edit menu to the right of that activity.
Click Edit settings in the drop down menu.
Scroll down to Turnitin plagiarism plugin settings and click on it to open up the menu options.