Plugin causes fatal Apache 2.4 error

Unfortunately, the directives “Order”, “Allow” and “Deny” are no longer available on Apache 2.4 servers unless the module mod_access_compat is installed resp. activated manually. In order to have your plugin run on all kinds of Apache servers, you will probably have to change the code that is automatically inserted into the .htaccess file as follows:

# Apache 2.2
<IfModule !mod_authz_core.c>
    Order Deny, Allow
    Deny from all
</IfModule>

# Apache 2.4
<IfModule mod_authz_core.c>
    Require all denied
</IfModule>

Also, you will have to provide some additional PHP statements for allowed IPs: "Require ip ".$ip. "\n";
as well as for disallowed ones:
"Require not ip ".$ip. "\n";

Hope this helps
– Hanno