VPN Error 812

Hi,

I setup VPN at one of my office Virtual Server. I assigned public IP address to it and tried to connect via PPTP under MS-CHAPv2 authentication method. But it generates error 812 I browse a lot and double check on my server both authentication are same. I disable Network Policy but same error. Please let me know what I am missing as this thing took lot of my time. 

Thanks

Jibran Ishtiaq