So it seems that the problem is with the lead or connection.
I plug my S-video/S-video lead straight into an S-video socket on the front of the TV so I don't have to make a choice. But there may be two kinds of Scart socket on your TV. There are on mine.
One Scart socket is for RGB (Games etc)and the other is for S-video (SVHS)inputs. I bet you've already tried both sockets if there are two. But if not try the other Scart socket and see if that works.