[Varstahl]

Try to log in www.primevideo.com to see if any error messages pop up. It only works with a valid Prime account, not a sub-account, and there are other restrictions which crop up from time to time. If you use the same credentials on www.primevideo.com, and it works, open an issue on GitHub and follow the instructions.

Edit: it might also be a change of Amazon's APIs, without logs and JSON data I can't tell you more.