Maybe a student needs to take an online quiz again. This tutorial will help you with granting one or more attempts. Steps 1-3 will need to be repeated for every quiz in the course for the student. Unfortunately there is currently no way to grant more attempts in all the course's quizzes for a single student.
Step 1: Go to "Moderate this Quiz"
Go to the quiz that needs an extension. On the top-right corner click on "Moderate this Quiz".
Step 2: Getting to the User Extension Menu
On the Moderation page navigate to the student that needs the time extension. On the far right corner of the row click on the pencil icon.
Step 3: Enter Additional Attempts
A menu will pop-up. There is a text-field for the item "Extra attempt" this is where you will place additional attempts. For example if students are given one for a quiz and you want to grant an additional attempt, you would enter 1 into the field. Click the Save button after entering the time to complete giving the student the additional attempts.