Unable to login to mapped domain

I have WordPress Network installed at http://www.wordpressya.com and I've added the domain http://www.sutebaquilmes.org as a site.

Everything looks good but if I try to login to their WordPress, I'm just redirected to the login page again.

In case you want to retest this:
User: sutebaqu
Pass: DunNK1Sw

Here are the last lines of our config file, in case it helps:

define( 'SUNRISE', 'on' );
define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', true);
define('DOMAIN_CURRENT_SITE', 'www.wordpressya.com');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);
define('WP_DEBUG', false);

/* ¡Eso es todo, deja de editar! Feliz blogging */

/** WordPress absolute path to the Wordpress directory. */
if ( !defined('ABSPATH') )
	define('ABSPATH', dirname(__FILE__) . '/');

/** Sets up WordPress vars and included files. */
require_once(ABSPATH . 'wp-settings.php');