Saving "Edit a subscribe page" resulting in a 403 Forbidden error

I’m trying to save a subscribe page edit after a CAPTCHA plugin addition but it is resulting in a 403 Forbidden error.

I have added the edit

public $session_name   = 'phpListSession';

and Mod Security disabled on the .htaccess file

<IfModule mod_security.c>
 SecFilterEngine Off
 SecFilterScanPOST Off

Any thoughts?