When you run into the issue that the NetworkManager is not starting your connection (nothing happens when you click on the VPN connection in the applet), you’ll see the following line in the syslog:
No agents were available for this request
When you start the connection from the CLI, you get the following error
$ sudo nmcli -p con up id YourConnection
Error: Connection activation failed: no valid VPN secrets.
Now, there are solutions available for password connection, but none when you work with certificates. You can use a workaround by editing the configuration file yourself. You can find it here:
/etc/NetworkManager/system-connections/YourConnection
Open the file and add or overwrite the following lines:
[vpn]
service-type=org.freedesktop.NetworkManager.openvpn
connection-type=tls
username=YourName
auth=SHA1
remote= ######
cipher=AES-256-CBC
comp-lzo=yes
cert-pass-flags=0
port= ######
cert=path-to-your.p12
ca=path-to-your.p12
key=path-to-your.p12[vpn-secrets]
cert-pass=YourPasswordForThisConnection
Restart your command, and VPN should be up and running.
Brain/Drain/Pain 