Amazon prime updated their app this year. Now I get subtitles in German. I have already set the language to English both in the app and on the Roku Ultra.
Also the Amazon Prime app now stops and loads a preview while trying to select a movie. This makes it impossible to browse for a movie because by the time you read a title the app stalls and waits for a preview to load before allowing you to continue. How do I go back to the Amazon Prime App last version that worked much better?
You cant revert to a previous app version.
Try turning the subtitles off and back on in app (verify its set for English, in app).
Check for Auto preview enable/disable settings in the Settings section of the Prime app.
Amazon codes/develops/publishes and is responsible for the Prime app - including the subtitles and auto preview behavior - you'll need to contact them about issues with each.