Hi Aggie123
Tv pictures come via rooftop antenna or via ethernet from your router .. so the cause is either network or a problem with your rooftop antenna .... check the co-ax cable ( especially at the end that plugs into the youview box ) and ensure your ethernet cable is connected correctly .. also if your using powerline adapters to connect the youview box ( which many customers do ) then ensure these are paired ok and were needed move them to a alternative socket ( avoid using power extensions ... try to plug powerline directly into the wall socket )
failing that wait for the OCE,s to see your post and allow up to 48hrs for a response
good luck Aggie123