Gradebook categories not showing up in User Report

The view in User Report defaults to hidden when grade items are hidden. This prevents grades from including items which have been hidden and graded. To change this setting, Click on Grades>Gradebook setup>Course grade settings

Next, scroll down to Overview report and change the default from hide items to show items excluding hidden items.

Change the setting and this should allow the Category averages to appear visible for your students to see.