When I try to set up payment with First Data, I receive an error

ALERT: For security reasons, Installation of this module is disabled until your Admin is configured for SSL.

I follow the instructions as follows

Change includes/configure.php and admin/includes/configure.php to:

// Define the webserver and path parameters
define('HTTP_SERVER', 'http://www.YOUR_SHOP.com');
define('HTTPS_SERVER', 'https://www.YOUR_SHOP.com');
define('ENABLE_SSL', 'true');

Having done both of these, I still receive the error message that Admin is not configured for SSL.

I have tested the site, https://www.apaspca.org and the ssl is working.

Any advice?

Thanks!