I bought the OLED55b7v at the weekend and it's awesome, the only issue I'm having is the Amazon app doesn't offer any 4k or HDR programmes whatsoever!
I've updated the app to the latest and updated the firmware as well (now on 4.70.65).
I uninstalled and re-installed the amazon app and still nothing above 1080p!
[edit to add] I should add, Netlix, Nvidia Shield and the xbox all work perfectly well with HDR / Doby Vision etc.[/edit]
Can anyone help?