Cannot get Verotel Plugin to work!

Wordpress Version 4.7
All WooCommerce and Verotel plugins are up to date.

My problem is that when I go to check out, it takes me to a page that says

Unknown website: There seems to be a problem with the sign up process for this website. Please contact the webmaster.

WooCommerce shows the cart empty and the order as being cancelled.

Any help would be great, I have been struggling with this all week. Verotel told me I needed to change something about

The woocommerce plugin does not work by default with CardBilling – you need to change the line:

$link = ‘https://secure.verotel.com/order/purchase?…….

and update the domain:

$link = ‘https://secure.billing.creditcard/order/purchase?…..

But I am not seeing this line in any of the WooCommerce/Verotel plugin files.

Thanks in advance, I hope this can help others who are looking as well.