Adam,
This might mean that your host has a reverse proxy, such as Varnish. If you have an option on your host’s control panel to disable Varnish or caching (outside of WordPress), that may help, and can prevent other issues as well. Although it’s fast, sometimes Varnish caches things that shouldn’t be cached on a WordPress site, and in the process, it changes the IP that Wordfence sees when a visitor arrives.
If that’s not possible, you may need to change the option “How does Wordfence get IPs” to X-Forwarded-For or X-Real-IP, depending on your host’s setup. You can confirm that it works by checking the Live Traffic page, to make sure your own IP appears when you visit a page in another browser. (Make sure that you are logged out in the other browser, since your own visits aren’t tracked when you’re logged in, by default.)
-Matt R