Whois shows that host to be on a Plusnet IP address.
Have you configured a static WAN IP address in your router?
If so check it's the one assigned to you, or better still remove it from the router the correct IP address should be automatically assigned.
If you don't have a static IP address from Plusnet, just reboot the router and you should be assigned a different one.
If none of the above help then you need to phone plusnet support.
