API Support for Product Add-on
The existing WHMCS version does not support API call if the product is setup as add-on. The reasons product add-on is a feature in WHMCS is to allow us to up-sell additional services to the clients. But if it's not supporting API call, it will make the entire user-experience to drops as those orders would need to be manually provisioned. Would love to see WHMCS be able to get this work out in coming 5.2 release.