Please configure the Client software with an IP address of the Host Server basically your Server IP address where SQL is installed. I have a similar issue with a 2 tier application where a user can access the Server through a client application on a LAN network and when connected to a VPN the and open the client app it gave me an error message so there was an option to configure the client app with an IP address of the Server, then we were able to access the Database over VPN connection. Thank You  ... View more