Thank you for your screenshot. That is highly unusual, and there appears to be an issue looking at the NaN value listed when you have no filters set:
Super Admin, Group Admin and User are the only user types. Are you referring to the Roles you can create for new users?
Please can you create me some troubleshoot logs, so I can take a closer look at what is happening when you go to the Users page and see no entries when no filters are set? This document explains how to do that.
I would recommend sending them to me in a private message, as they could include some sensitive information about your setup that you may not wish to make public.
Many Thanks.