I caot access VPN via tethering to my Phone

I get the error below whenever I try to coect to VPN via tethering to my Phone. Using the VPN via Wifi works fine. Can you please me know if you have encountered this before or possible resolution by editing setting or contacting the Phone service provider.

Error :- Secure VPN Coection Terminated by Locally by the Client Reason: 429 unable to resolve server address

Laptop :- Dell E6420 Ruing 32bit Win 7 Pro Phone is Lumia 640, ruing Win 10 test build VPN :- Cisco solution Phone Service Provider :- Voda Phone UK

Any and all help welcome. This is my first post so if your require more data then please let me know.