Hi,
Just checking your problem with Nicolas. I will try to explain it clearly.
The configuration of your plugin is wrong but it is something that we can't do anything because it requires communication with Paypal.
When someone buy something on the internet using paypal, he will receive an email, directly from paypal.
This paypal (not sent by HikaShop) contains a "Transaction Id" ; the information that Paypal needs.
Thanks to this "Transaction Id", paypal will be able to know to which one the payment has been made.
Some extra information:
if you are in sandbox mode, no real payment will be made so, you can't see any transaction or payment with the real/live account.
The sandbox is a test mode so, it can't make real transaction, all are "fakes" for test purpose.
So if you want to make a real payment, you have to not use the debug/sandbox in paypal.
Regards,