Apple TV won't work after router change

I Have used Apple TV for a couple of years with no problems. Today I had a new router installed, tried to watch something from my iPad and the Apple TV won't work. I can't even get the menu to come up so I can select the new wifi code.

I am sure the battery in the remote works, as the white light on the Apple box flickers when I press 'menu' etc.

Any suggestions would be gratefully received.

Thanks.