Amazon Android app appears to not sell digital content
It appears that Amazon and Google’s feud over payments appears to have come to a head as there is now no way to purchase digital content in the app store. At least no way I could find. Physical content is still there and processed normally, but digital has gone away. You can see it, there’s just no buy button.

Since April 2022 companies with a turnover above a million USD pay 30% commission on in-app purchases on digital goods and services. As reported by the BBC, Amazon said the change was made in response to Google Store policies.
In-app physical product purchases were exempt from Google’s fees last I could locate.
You can still purchase digital in a browser or at a computer and access via Amazon apps, but the convenience is now gone.
[9to5Google]