Unable to connect to company VPN

[#1]

The VPN I use adds a DNS server to the connection so that the DNS servers configured on the PC are not used. In any case the default PC configuration would be to use the router DNS (which in turn would use the PN servers).
If the router interface can be accessed while the VPN is connected I would have expected using the routers DNS as the local LAN traffic won't go through the VPN tunnel.

[#2]

Thanks oldjim but unfortunately my PC is locked down.  This issue has only just started occurring after several years of connecting successfully from home using my company laptop - thats why I'd expect it to be something Plusnet have changed.

[#3]

Can you run a Command window and post the result of:
nslookup <the URL of the VPN access page>
nslookup <the URL of the VPN access page> 8.8.8.8
nslookup <the URL of the VPN access page> 208.67.222.222

[#4]

Interestingly today I am working from home with no problems!  No changes made at my end.  So looks like whatever the issue was, it was temporary.  Thank you all for your advice.