If the grade book is not available or provides an error when selected, there is usually message on the screen like this, follow the steps below to correct.
Step 1: Open the grade book and go to the column organization under the manage tab.
Step 2: Choose Column organization and then submit it, no need to do anything else on the page.
3. Reopen the grade book by clicking on Full Grade Center, you should now see all of the students and grades.