In the My Studies Course management panel  select Course Tools> Turnitin Assignments

Select the submission point and then select Sync Grades.

That’s it.

Who does this?

Turnitin lives outside of My Studies and every now and then the two get out of step and need a prod.
If the post date has arrived and students say they can’t see their marks it could be because the grades aren’t sync’ed.

Sync grades is a way to force the grades from marked submissions that have reached their post date to the Grade Centre.