Register Amazon Prime Video on Smart TV?

I have a small second TV from Kendo (24 LED 3191 T) and have already registered with Netflix without any problems. In order to watch the BL relegation games, I also wanted to register on Amazon Prime Video, but that doesn't work (with this TV?), Even though it has pre-assigned buttons for both services.

To log in, I should enter the code shown. There's just no field here where I can type in this code. The only thing that goes on this login page is generating a new code or completely back. The numeric keys of the FB, which are alternatively assigned letters as on the cell phone, show no reaction.

Is this a quirk of this TV or didn't Amazon Prime program properly?

You have to log in to Amazon by computer (amazon.de/mytv) and enter the code shown there. Then the TV is registered and you can watch everything on Prime.