When you buy an extension, even if the extension is good you may be blocked because you need support. There are always points you cannot find out yourself.
I'm from France and setting a Joomla-CB-Opencart website with extended Affiliate system. This is not so simple.
I bought an Opencart Multitier Affiliates extension. The programmer took contact with Mijoshop.
Mijoshop support has programmed and tested a special adaptation for me to allow the creation of the tables of the Affiliates extension and the integration into the Joomla-Mijoshop-Opencart boutique. And it was only in several hours !.
I can write a Trigger to register in OpenCart through CB Registration but I did not know exactly which PHP I had to modify. Mijoshop has provided immediately the infos.
That is true support. I'd never seen before such quality of support. Still a lot of thanks.