How to solve the problem of combining IAP and Amazon?

Question

Unity

I wanted to post my game on Amazon, everything went through and checked, but I stalled in one place, they all write to me that the IAP does not work for them, that is, the purchase button does not work ...

spoiler

Amazon Developer Support

Hi,
Thank you for writing in. We have retested your app and observed the following test failure(s):
Issue Description: App button is not responding.
Steps to reproduce issue:
1. Install and launch the app.
2. Tap on Shop.
3. Tap on any IAP to purchase.

Actual result: Observe that the app button is not responding, unable to purchase the IAP.
Expected result: App button should respond and user should be able to purchase the IAP.

Affected device list:
Kindle Fire HDX (2013)
Kindle Fire HDX WAN (2013)
.........................

at the same time, the same game, the same installation file, passed the test on Google Play perfectly and is now in the store there, downloading, all buttons are checked (including purchases), and on different phones I checked exactly the purchase (that is, I bought game items), everything is ok, that amazon does not like me xs ...
As I understand it, you need to use something else for the IAP place, or how else to solve this problem?