Hi @jovanv,

This issue is probably caused by a server misconfiguration, not by our theme. The “Not Found” error shown by your browser seems to be displayed by your webserver instead of WordPress. It’s like your browser is not able to reach WP when you enter the register URL. So, we advise that you contact your hosting service support to request for more help.

For better debugging purposes, please first navigate to “Settings > Permalinks” and make sure everything is properly set. You could also download and activate the following to flush the rewrite rules set on your website:

Rewrite Rules Inspector

If that’s not solving your issue, please activate logging on your website, just turn WP_DEBUG to true, like following:
define ('WP_DEBUG', TRUE);
You will find this constant in your wp-config.php file.

More on this in the following topic: https://codex.wordpress.org/Debugging_in_WordPress

Then, please deactivate all plugins except BuddyPress, activate a default WP theme (i.e. Twenty Seventeen) and then try to reach the registration page. This may confirm that the problem is related with your configuration and it might give you the necessary error logs to transfer to your server hosting support.

Finally, please also check the WordPress prerequisites here: https://wordpress.org/about/requirements/.

For better performance (and better security) we obviously recommend the version 7.2 for PHP. Nevertheless, if this is not possible for you (server type, incompatibilities with plugins, etc.) we recommend at least version 5.6.X.

We hope this will help.

Cheers,