AOL users can't add products to cart
The reason if the problem is AOL uses different REMOTE IP addresses for HTTP and HTTPS connection.
Remote IP address and user agent are being used for secure reasons to generate a session ID in Avactis. So if any person intercepts a session ID of another customer, he/she won't be able to use it to see confidential information and login to the Admin Area.
So, to make AOL works it requires to exclude the IP address checking from the session id hash generation, but this will decrease the level of security.
If you want to do these changes anyway, open the file avactis-system/core/session.php file and remove or comment out the following 2 lines:
! @array_intersect($_SESSION['REMOTE_ADDR'], $current_ips) ||
$_SESSION['REMOTE_ADDR'] = $current_ips;
The other way to solve the problem is to enable HTTPS for entire storefront. You can do it on the Admin -> HTTPS Settings page in your admin panel. Note that it may cause slowness of your site because it requires a time to encode the pages.