AppleTV Settings not working

Hi there, when I try to open any App on AppleTV, it tells me the following error:

'Connection Error. Check your network settings and try again'

Unfortunately I can't get into the Settings App as it tells me the same error!

The TV is an old Panasonic (not Smart TV) but the AppleTV was once working on it fine.

Is this something to do with my modem/wi-fi settings, or do I need to reboot Apple TV (I have already turned it on and off a few times).

Please help