Unable to connect to VPN using gnome-network-manager

In my case selecting the password option Store the password for all users got it working. All other options produce the mentioned error.

I just had the same issue and Plant Maven's answer was correct.

Instead of deleting the config files in /etc/NetworkManager/system-connections/ I moved them to another folder, so I could compare.

The only difference between the old config file and the new one is in a VPN connection I just re-created from scratch and it's the UUID.

No idea why the old file wouldn't work. I suspect it's something related to the keyring.

sudo apt-get install --reinstall network-manager

After running this command , I tried connecting to the vpn service, I was thankfully once again prompted for my vpn password and able to connect to the service.

After some weeks, I still have issues sometimes. When I log out and log in it resolves itself most of the time. I am using WICD network manager also now, due to sometimes wifi stops working altogether !

I just rm'd all files in /etc/NetworkManager/system-connections/ and restarted Ubuntu 14.04. Problem solved. I know it was the last software update because I updated and shutdown. The next time I started up Ubuntu, the network kept dropping connection.