See below from Adriel:

"NationBuilder allows you to restrict access to certain pages or to complete sites that are under development. If pages are showing a login, that means you have restricted access. For the sitewide settings, change this under Pages > Settings and change your drop-down to “anyone.” If individual pages have restrictions, changing the sitewide settings will not remove those restrictions. Check under Pages and if any of your pages has a lock symbol next to it, that means you have login restrictions on those pages. Click edit on each page with a lock and you will be able to change those pages to “anyone” as well."