Config import on network-manager-openvpn
Solution 1:
Try connecting to VPN from command line. This will make sure that the problem is with NetworkManager and not something else. You can connect from command line using:
openvpn --config /path/to/config.ovpn
You may need to run this command using sudo.
If you can successfully connect from command line then try adding yourself to netdev group and uncheck Available to all users in vpn settings window in NetworkManager and then try connecting using NM.
Solution 2:
I think tail -f /var/log/{syslog,messages} followed by reconnecting the VPN could give some answers.