With help ours software (BookLibrary e.g.) all payments user do on real amazon.com host. BookLibrary not take any payment.
When on yours site, some user press button 'Buy from amazon' - he go to Amazon.com with yours parameters - what you set for amazon associate program - in BookLibrary Bakend setting. next all do Amazon.com. They connect any user shopping with yours account.
Yours Amzon associate parameters - you add to any "[ Buy from ] link:" - at time when you do "fetch info" for every book from amazon.
Please go to BookLibrary any book details and check "[ Buy from ] link:"
There are you must find some thing like:
there are you can see
These parameters from yours BookLibrary Backend amazon setting.
If there are exist in yours BookLibrary setting and Book details - please go to amazon support - and ask from them