Plusnet Hub One - disconnected drives

[#1]

Staying with Plusnet I have just upgraded from ADSL to fibre and been provided with a Plusnet Hub One.  From one ethernet port, Lan 1 I have a cable going to another room and via a hub have a desktop computer and a D-link NAS connected.  The computer connection is fine but the NAS is disconnected even though the green ethernet activity led on the NAS is flashing. 
In the computer (Windows 7) the NAS is shown with a red cross, if it is double clicked the error 'the network path was not found' appears.  The NAS is never turned off.  Does anyone understand what is happening and how I can reconnect the drive?  (I didn't have this problem under ADSL and the Netgear router I was using.

[#2]

Hi
Is the NAS set to a static IP address on a different range to the new Hub one IP address range?
Most LAN clients use DHCP to get an IP address assigned by the router automatically.
This could be undesirable for a NAS as the IP address could change every time it was powered up.
I believe Netgear routers use an address range of 192.168.0.x (x =1 to 254)
I suspect Plunset Hub ones use the same address range as BT home hubs 192.168.1.x (x =1 to 254)
If your NAS has a static IP like 192.168.0.50 but your Hub One operates in the range 192.168.1.x nothing will connect to the NAS.
Use your old router (do not connect to the phone socket) to connect the PC to the NAS  via Ethernet and check the IP address settings.
Richard

[#3]

If the NAS has an option to obtain it's IP from DHCP use that temporarily until you have it up and running on the new router.

[#4]

Thanks for the ideas - the range of ip addresses is different - I may have set a static ip address for the NAS but it was a number of years back! - I seem to have solved the problem by powering down and disconnecting everything from the mains power apart from the router before I went out. When I came back and turned everything back on it all worked 
I hope it still all works tomorrow!

[#5]

That suggests the NAS is set to get it's IP from DHCP and powering off and on forced it to get a new IP (in the correct range).