Why did my student’s submission not go through when it looks like it was submitted before the due date?
If you chose to require your students to click the "submit" button for them to confirm when they were sending their final draft, the student will have to hit the submit button before you receive it as their final draft.
EDITING ASSIGNMENT MODULE VIEW
This means that when a student submits their final draft, they would need to not just drag/drop their document, but also submit their final draft.
For this reason it still has the "Submit assignment" button visible.