You may be using an Apache web server and have configured something in the .htaccess file which instructs that only requests from localhost, 127.0.01 or the IPV6 equivalent are answered. It is also possible that you have entered a similar rule for another web server you are using.
Or you may have entered in your router that the computers are allowed to access the Internet but are not allowed to communicate with each other.
Or you may have uninstalled an add-on on your Dokuwiki that allows you to configure from which IP or IP ranges the Dokuwiki answers requests.
In operating systems such as Windows and Linux, there is also something like an .htaccess file where you can set a few DNS configurations that can also have this effect.
Or have a look at your Dokuwiki under "Admin--Configuration" to see if there are any entries with "127" in them.
Or, or, or