Hey Truonglv so I made sure I had the most recent update, which seems like it was this past Friday - but the version number never changed. However, I have that and I went into permissions and set the permissions to unlimited across the board for all my permission groups.
I went back into the groups and I still cannot see anywhere, in any of the menu options - drop down menus - anywhere to invite members.
Where should it be? I remember it being right above or below the share group section.