On the image you posted above 
Where have you plugged the other end of that cable?
The router in the link https://www.tp-link.com/uk/home-networking/wifi-router/archer-ax73/
Has the following ports on the back:
- One Blue Wan (RJ45) Port
- Four Yellow Lan Ports labelled Lan 1 to 4
- Power input
Now Broadband uses what is called DSL technology to provide internet to your property, which is carried over the copper phone system, this uses a high frequency signal which is added to the phone line , there are two types of this:
ADSL which stands for A-symmetric Digital Subscriber Line is where the internet signal is added to the copper phone line at the local telephone exchange, now sell this as Fab fibre and it typically has download speeds of around 12mbps ( although can be anywhere from 0.25 to 18) and typically 5mbps up as the download is faster than upload its not symmetric hence A- Symmetric , this operates at a higher frequency than voice traffic so it can transit more data
VDSL : Very High Bitrate - A symmetric Digital Subscriber Line similar to plain old ADSL where the internet signal is added to the phone line, but this happens at a street cabinet closer to your home so the frequency can be higher and in turn more data can be transmitted, this is known as Fibre to the Cabinet (FTTC) and confusingly sold as fibre
With all that out of the way...
As mentioned what is called a router is actually an all in one box in the case of Now and other FTTC containing:
A Wifi Access point (AP) this provides the wifi signal
A router - this routes the internet/data traffic over the network between the yellow ethernet ports and the wif access point
a modem this modulates and de modulates (hence the parts Mod for modulate and Dem for de modulate) the internet signal as used by Now ( and others) into something that your devices ( and the wifi access point) can understand
A firewall, this can stop some nastys from the internet getting into your netowrk
A network switch , this switches data between the ports and the wifi access point.
What you have is a device that lacks a modem , and can not be used with Now or any other DSL service on its own , it will need a modem connected to it.
The Now router while in theory should be up to this should work by connecting a yellow port on the now router to the blue WAn port on the tp link device, however you will end up with two devices, and as the now router is rubbish and doesn't support modem only mode you will have another little nasty called double NAT
What you need is a DSL modem/router.
hope that explains it a little, but as it is that TP link device will not work on its own
