Hello, I experienced the same problem with the anyone can register, tried to modify DB through the phpMyAdmin app and found that everything was as should be, deleted all the plugins. So, i created a new subdomain with an new WP installation, mark the check box at first place and then installed the plugins 1 by 1. When I starte to configure Really simple SSL I found that by default there is an option that make the “anyone can register” to be on blank on >setting > Hardening > Disable “anyone can register”. So, in my case it was something really simple.
Hope this info help.
Regards.
