How do I re-activate remote for Apple TV

I have an Apple TV 2 and 2xremotes (plus my iphone remote App) and none of then will connect.

One of my remotes won't scroll upwards so I found an old white one and then the battery went on it so I hooked up my iPhone but the other night something happened and Apple TV is no longer listed in the Remote App only Home Sharing. So now I can use my Apple TV. (Except by using Home sharing and Airplay, but I am unable to use Netflix.)

How can I fix this?

I tried holding the menu and rewind buttons while standing infront of box, but nothing happened.