Comment 58 for bug 1294899

Found a manual fix for my specific case; it may be useful for others, so let's share it.

I'm running network-manager-gnome 0.9.8.8-0ubuntu4.3 and I was having the same issue while importing a connection from an .ovpn file (no message, no error, nothing at all). After I checked the file contents, I found a short message instructing to switch on a commented line for the tls-remote parameter if running openvpn 2.3+ (which Trusty Tahr does); once I did that (also disabling the original one), I was able to import the connection and the VPN was working correctly when I enabled it.

Line for old OpenVPN version reads like:
tls-remote "/C=xx/L=SOMETHING_HERE<email address hidden>"

Line for new OpenVPN (2.3+) reads like:
tls-remote "C=xx, L=SOMETHING HERE, O=COMPANY NAME, CN=ANOTHER-VALUE-HERE, <email address hidden>"

Please note my .ovpn file didn't include embedded certificates or keys, they were provided as separate files from the very beginning.

Hope it helps.