You will need to activate Attempts reopened in the assignment settings.
Turn editing on.
Select Edit alongside the relevant assignment on the module homepage to edit the assignment.
Select Edit settings.
Scroll down the page to Submission settings.
Select the relevant option under Attempts reopened:
Manually (Lecturer reopens the assignment for the student)
Automatically until pass (Assignment automatically reopens until the student reaches the set passing grade.
Set the Maximum attempts to indicate how many times the student can resubmit. NB A student's original submission counts as an attempt so you will need to set Maximum attempts to at least 2.
Click Save and display.
The lecturer or course officer has to reopen the assignment for the student.
Click on the relevant assignment from the module homepage. Click on View / grade all submissions.
Click on the Grade icon alongside the relevant student.
Scroll down to Attempt settings.
Set Allow another attempt to yes.
Click Save Changes.
The student will now be able to resubmit their assignment but only up to the cut-off date in the assignment (if set). If your resubmissions are due after the cut-off date you will need to use the grant an extension function to enable the students to resubmit.
Automatically until pass
In this case the assignment automatically reopens until the student reaches the passing grade which has been set by the Lecturer in the Gradebook.
From the Dashboard, click on the Grader Report icon.
Select the Setup tab.
Scroll to the relevant assignment and then choose Edit > Edit settings.
Click Show more and then enter your Grade to pass. Scroll to the end of the page and choose Save changes.