I'm assuming you are using a web-browser to access the tplinkdns.com link from outside your network.

This is basically asking your browser to say 'show me the webpage at this address". Your router is currently responding with the equivalent of "What webpage? There isn't one here except my admin area."

This means you'll need to perform something called 'Port Forwarding' on your Sky router, to tell the router that any requests for a webpage go to your NAS, which can then respond with "I have a webpage, it's this one" and show the NAS login page.

You will need:

- The login details for your Sky router (I assume you have these if you've fiddled with the DHCP server already)

- The internal IP address of your NAS (usually found in the NAS settings area, or you might be already using it to connect to the NAS internally. It'll be something like '192.168.1.xxx')

Then perform these steps:

- You'll need to log into the Sky router, locate the Port Forwarding section (see the associated manual if you can't find it: https://www.sky.com/help/articles/download-sky-broadband-user-manuals)

- Enter the external port (80 usually, but I'd advise against using this as it's a common port for trying out attacks, try a random number like 9000 and note it down for later)

- Enter the internal IP address of your NAS from earlier - Enter the internal port 80

- Save the changes

- Try connecting again from outside, but this time using: http://xxx.tplinkdns.com:9000

@richpriest 

Thanks for the quick (and detailed) response.

Just a quick question when setting up the port forwarding, the only device that shows up is main Deco (which is attached to the Sky router). 

The NAS is not showing up as connected to the Sky Hub. 

So I'm not sure how I would enter the details of the NAS in the SKY hub admin panel...

I am able to view the NAS through the Deco app only (I have used this to provide a static IP)