Currently the code trims off the last 3 characters to find the correct datacenter for API actions.
New Mailchimp accounts could be on a double digit datacenter, for example us12. The correct path for my Mailchimp account would be:
https://us12.api.mailchimp.com
I just edited the includes/aksh_widget.php to use the last 4 characters, really it should explode the string at the – and use the 2nd portion.
if( strpos( $api_key, '-' ) !== false ) {
$api_url = 'https://' . substr( $api_key, -4 ) . '.api.mailchimp.com/2.0/';
}