Once students have already taken a graded quiz, any changes that affect the quiz score such as deleting questions or answers, or manually entering a new mark typically do not work. A rocket icon appears in the gradebook column, indicating the quiz has not been fully graded. To regrade or modify a quiz that students have already taken:

1. Use quiz regrade
Edit existing quiz questions and tell Canvas to recalculate student grades.

2. Use quiz fudge points
Manually add or remove points from the student’s overall quiz score. This feature is only available in SpeedGrader.

3. Add a ‘no submission’ assignment
Create an assignment worth the number of points that you need to give the students additionally for the quiz. Add the assignment into the same assignment group as the quiz. Navigate to the gradebook, mute the assignment and enter the points into the column. To input the same score for all students, set a default grade for the assignment. You may need to consider how your assignments and weightings have been organised.

The suggested options may only work with certain scenarios. Please contact Staff Service Centre (SSC) for further assistance.

Read more on Canvas Community:
What options can I use to regrade a quiz in a course?
How do I use quiz fudge points in SpeedGrader?
How do I set a default grade for an assignment?
How do I create an assignment?