Mapping shared drive with VPN access
I'm the only person in our (small) company with a Mac and I work remotely. I have successfully accessed my company's VPN using Network Connect.
I'm now trying to map the shared drive.
Under 'Go' > 'Connect to server' I've entered the server address ("smb://....." etc) as it has been given to me. When I click connect I get an error "There was a problem connecting to the server '[ server address ]'. The server may not exist or it is unavailable at this time. Check the server name or IP address, check your network connection, and then try again".
I've tried a number of variations of the server address - none has worked.
In Finder, under 'Shared drives', all I can see is an empty 'Servers' folder.
When I'm in the office on the company's internal wifi, we have been able to map the drive. But nothing so far has worked remotely, remotely.
Can anyone suggest a solution?
MacBook Pro (Retina, 13-inch, Mid 2014), OS X El Capitan (10.11.5)