Prime Video fails on Apple TV

I've used the Amazon Prime Video app on Apple TV without incident for a couple years, but recently Prime Video fails to open. All other Apple TV apps work fine. I tried checking for an update to Apple TV software, but I'm apparently running the latest version (16.2). I tried deleting and reinstalling the Prime Video app and restarting the Apple TV 4K device but this did not fix the problem. When I try to open Prime Video, sometimes I get an error message (in German!) and sometimes there is just a black screen. I never see the sign in screen. Since all other Apple TV apps work normally, and I can't get any help from Amazon support, does anyone in Apple community know how to fix the problem?