A common thing we run into is Mac users who can't connect to the servers and there's no obvious cause. The Mac firewall will block connections without ever alerting you.
Try this: start a connection to the VPN, then go to System Preferences> Security and Privacy, and unlock the UI by clicking the padlock in the bottom left.
You should see a notification saying something along the lines of 'system process has been blocked' and you'll see an “Allow” button next to it. The application may be tagged as Unnamed from an Unknown developer.
Allow the application and restart the computer. This should allow you to connect.