Most likely it is because you have students that have already attempted the Quiz. You will need to delete all of the attempts if you need to add/remove questions from a quiz.
To delete all student attempts:
Select a Quiz and select More. Then select Overrides from the drop-down menu. This provides links to to User overrides. Avoid Group overrides for managing resubmissions, extensions and reasonable adjustments as students can see the members of the groups.
Set the User overrides required.
If your quiz contains all the questions in one page you can easily print it from your browser. Open the Quiz, select Settings and select Preview from the menu. Use the browser settings (e.g. in Chrome) and select Print. Using this option you can also print the quiz to .pdf. If your quiz contains several pages, you will need to print them one by one.
Review your Quiz and verify Moodle has enough questions from each category of questions it will be pulling from. You may have inadvertently selected more questions than what exists in the category.
Also, make sure you're not pulling questions from a category that has zero questions. Because you are picking random questions, rather than a specific question, it may not be apparent at first that you have run out of questions to ask.
If you would like to use a quiz that is not graded, you have two options:
If you would like the quiz to be graded but not to count in the final grade, you could set your grading report and include the Quiz in a formative assessment category.
You can not remove a question once a quiz has been taken by one student or more. However, you can change the score and flag the question so you know it has problems.
Set the score for that question to 0. Find the question in the Question bank. Edit the title (Do not use in Bio101). Or if you do not share the question category with other teachers, create a subcategory, move the offending question there, and create a better question to replace the one you just moved. Create a new Quiz and if necessary hide the old Quiz.
This situation is produced when you select Attempts must be submitted before the time expires, or they are not counted from the options under When time expires in the Timing settings in the Quiz activity
In that case, if any student fails to submit the quiz before the time expires, their attempts will display as Never submitted and they will not be automatically marked.
The solution to this problem is complicated and involves changing settings in a live activity, we recommend logging in your query in IT Self Service Portal.
The solution will require staff with Programme Administrator rights to: