“Anyone Can Join” Option Missing

I am trying to fix the user settings with my multisite. I want someone to sign up on one page and become a member on all of my sites. However on my main site, the Anyone Can Register Button is not there at all.

The option is available on all of my other sites, but not my main one. There’s been a notice about it on the back end for 2 days now. Every time I click the general settings link the Anyone Can Join box is still nowhere to be found.
What should I do?