Gradebook does not include ungraded items in the course grade calculation. This could result in a higher course grade average for a student if they have incomplete items. To include a Gradebook item in the course grade calculation, enter a grade of zero or higher.

To enter zeros for ALL Gradebook items that have not been graded, use Set Zero Score for Empty Cells. You can not this action once done, though can you still manually adjust scores in each cell if you discover that you've made an error.

See How do I set empty cells to zero for a single grade item? to take this step for just one item in the Gradebook.

Warning: If your gradebook contains one or more items pertinent to only a subset of the entire class, using the function below for setting a zero score for empty cells will adversely affect scores for students not included in those items. For more details and guidance, refer to the article, How should I handle gradebook items not pertinent to the entire class?