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