Having a bit of a pain with this. Unless they go to the grade book teachers don't seem to be able to change the grade. It states the assignment is not accepting submissions when it is. Bizzarely it seems hit and miss (on the same assignment submitted at the same time) and some of them are changeable. The drop down does not appear. I've attatched a screenshot of the screen I'm on about as I'm rushing this a bit sorry!.