I am having some issue with Azon Authority Checkout. Almost 40% of the products added to the Cart will not show up when you go to Checkout and redirected to Amazon Shopping Cart.
In some cases, you may need to post products as External/Affiliate, as for some products, Amazon will disable the on-site cart.
We have found it best to have this setting enabled (Settings > Advanced) as shown in the screenshot below.
You can change products that are already imported to External/Affiliate in WooCommerce (unfortunately one at a time) shown in the second screenshot below, or delete and re-import them.
Please also do the following troubleshooting steps in their entirety: https://kb.imsuccesscenter.com/kb/before-submitting-a-ticket/