In ArcGIS Online, Organization/Members, the members list contains some members are shaded/grayed out as shown in the attached. All the elements are still active for clicking in either case. But why is the row shaded out?
I was able to reproduce the Grayed Out user by disabling a user. Is this member disabled? You can check by selecting more options, and if they are disabled it will show "Enable member" in the drop down.