After the installation of the newest update, The invite button is "locked" or Greyed out. I think its because of the fix: "Invite icon will now lock when realm is at max compacity"

I think this is the main problem. It doesn't affect people joining, but the invite button is

un-accessible no matter how many players there are to 1-10 (max).

This only affects realms and maybe Custom Friend-Made Servers.

Example screenshot: