The attendees button is no longer showing on my events. I updated to version 4.04 from 3.x and now my attendees button no longer is displaying. I tried different themes, but I am experiencing the same issue with all.
There was a patch mentioned in this post: https://www.joomlart.com/forums/d/6944-attendees-button-not-showing-in-4-0 but it also did not work for me.