In the Information tab of the module you have the following message:
The order state: "Pending Shipment" automatically send an email. This is not allowed by Amazon. Please configure an another order status.
By default the order status “Shipped” on Prestashop sends an email to the customer, which is against the rules of Amazon, so that must be customized in your Prestashop configuration for the module.
Please go to the Orders tab > Orders Statuses, click on Add:
Unselect Send e-mail and select the same boxes as your usual shipped status:
Please go to the configuration of the Amazon module, in the Settings tab and select the status that you’ve just created:
The status order shipped will not send email “store” to the client, the warning message will disappear.