I'm running Arch Linux, and recently updated the whole system.

Now I every time I connects to VPN with `nmcli` command, if it fails, I couldn't figure out the reason:

```
NetworkManager[15967]: <info> VPN plugin state changed: starting (3)
NetworkManager[15967]: <info> VPN connection 'XXX' (Connect) reply received.
NetworkManager[15967]: <warn> /sys/devices/virtual/net/ppp0: couldn't determine device driver; ignoring...
NetworkManager[15967]: <warn> VPN plugin failed: 1
NetworkManager[15967]: <warn> VPN plugin failed: 1
NetworkManager[15967]: <warn> VPN plugin failed: 1
NetworkManager[15967]: <info> VPN plugin state changed: stopped (6)
NetworkManager[15967]: <info> VPN plugin state change reason: 0
NetworkManager[15967]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.

```

Prior to the upgrade, I can see error messages from pppd, e.g "You're already logged in bla bla", now every helpful message is gone.

Any ideas? Why is the connection failed?