Issue: After upgrading to Windows 10 the VPN does not connect to the server (SBS 2011) anymore:

Error: The connection was prevented because of a policy configured on your RAS/VPN server. Specifically, the authentication method used by the server to verify your username and password may not match the authentication method configured in your connection profile. Please contact the Administrator of the RAS server and notify them of this error.

Easy to resolve:

On client side go:

  • Go into Control Panel\Network and Internet\Network Connections (the old Networking control panel, not the new one).
  • find the vpn connection and open it's Properties dialog.
  • On the Security tab make sure that "Allow these protocols" radio button is selected and that the Microsoft CHAP Version 2 (MS-CHAP v2) checkbox is selected.