Did you try to view Netflix using your Apple TV? Did you manage to logon to Netflix, but does the Netflix app fails to stream any content?
In this case, you might see this error message presented by the Netflix app on your Apple TV:
This message tells you, that the Netflix app on your Apple TV fails to connect with a certain server of Netflix.
In case you use a Fritz!Box router or some other router with a parental control system, please check its respective settings.
If parental control is enabled, chances are good, that Netflix is black-listed by the parental control system. Consequently, streaming of Netflix content gets blocked by your router.
To make sure, that the parental control system really is the problem, disable the parental control system and try to stream a movie using Netflix.
If, after that, you are able to view movies using Netflix, you just discovered the problem. Congratulation!