Then if that fails, do this.
It doesn’t matter what the TV is and it doesn’t need to support the Now app for itself, as long as it has an HDMI socket into which you have plugged a stick or other device that does support the Now app.
Now used to have a Stick you could buy, and before that, boxes you could use, but they no longer supply these, only the Now router, which is quite separate from any of the streaming devices.
I’m not sure if you have a Now Stick there or not; have you got one which you are failing to get set up, or what?
If you haven’t got a Now Stick, then a Roku device or an Amazon Firestick can be used to get Now. Curry’s have the Roku Express; HD for £20, 4K for £30. Firesticks start at £38. I prefer the Rokus not just on price, but because of their much less cluttered user interface.