How can I have my money back?

I purchased the premium plugin to use the bulk order functionality that uses the official AliExpress API. But the plugin doesn’t work properly and I can’t connect to AliExpress. I saw here on the forum that other customers are having the same problem and you say that it takes several attempts to get an access token. I use Dsers and never had this problem. So I want my money back, the plugin doesn’t work properly. How to get my money back?