If the status shows "unknown", it's likely that:

- the VPN credentials (user/pass) are incorrect. Clear credentials, insert them again making sure they are correct (note that password is case-sensitive), save credentials and restart the browser. Retry to connect. 
- you are using a security software/anti-virus which hijacks the SSL browser connections. For example, BitDefender Internet Security. From its settings, disable "SSL inspection". 
- other addon/extension interfers with the proxy settings. Disable any other plugin/extension that provides a proxy service.