The default letter scale (A+-F) has been removed from our Moodle system. It did not accurately calculate category/course aggregations when combined with number grades.
We recommend you use numeric scales for marking grades. If you want to display letter grades, there is an option for that in your gradebook settings.
If you prefer to enter grades as letters, you can create your own letter scale for your course, knowing that you should be careful if aggregating.
Please contact Jessica Schlueter if you need assistance with either of these options.