Thank you for your post.
You can reset the assignment for an individual student by following these steps:
1. Open the Gradebook.
2. Search for the student's first name, last name, or email.
3. Click on the student's name, and then on the name of the assignment.
From there, you should see the Reset or Allow Access button, and the student's previous attempts. You can also extend the due date from that page.
I hope this helps. Please let me know if you have any questions. Have a great day!