14.04: Clicar em uma conexão VPN no menu de ícones da rede não faz nada

Question

Isto é idêntico a ( Conexão VPN aberta não trabalho após a reinicialização do Ubuntu 14.04 ) com a única exceção de que é uma conexão PPTP e não OpenVPN.

Normalmente, quando clico em uma conexão no menu, o ícone muda para um ícone híbrido "conexão Wi-Fi + bloqueio" e, após alguns segundos, uma notificação informa que ele está conectado. Agora nada acontece.

Aqui está o log:

jon@jon-ThinkPad-T430:~$ grep VPN /var/log/syslog
May  4 06:53:18 jon-ThinkPad-T430 NetworkManager[901]: <info> VPN: loaded org.freedesktop.NetworkManager.pptp
May  4 06:55:15 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN: loaded org.freedesktop.NetworkManager.pptp
May  4 18:40:26 jon-ThinkPad-T430 NetworkManager[825]: <info> Starting VPN service 'pptp'...
May  4 18:40:26 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 7685
May  4 18:40:26 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' appeared; activating connections
May  4 18:40:26 jon-ThinkPad-T430 NetworkManager[825]: <error> [1430754026.793268] [nm-vpn-connection.c:1374] get_secrets_cb(): Failed to request VPN secrets #2: (6) No agents were available for this request.
May  4 18:40:32 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' disappeared
May  4 18:40:34 jon-ThinkPad-T430 NetworkManager[825]: <info> Starting VPN service 'pptp'...
May  4 18:40:34 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 7688
May  4 18:40:34 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' appeared; activating connections
May  4 18:40:34 jon-ThinkPad-T430 NetworkManager[825]: <error> [1430754034.875066] [nm-vpn-connection.c:1374] get_secrets_cb(): Failed to request VPN secrets #2: (6) No agents were available for this request.
May  4 18:40:40 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' disappeared
May  4 18:42:31 jon-ThinkPad-T430 NetworkManager[825]: <info> Starting VPN service 'pptp'...
May  4 18:42:31 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 7701
May  4 18:42:31 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' appeared; activating connections
May  4 18:42:31 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN plugin state changed: init (1)
May  4 18:42:31 jon-ThinkPad-T430 NetworkManager[825]: <error> [1430754151.206401] [nm-vpn-connection.c:1374] get_secrets_cb(): Failed to request VPN secrets #2: (6) No agents were available for this request.
May  4 18:42:36 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' disappeared
May  4 18:44:50 jon-ThinkPad-T430 NetworkManager[825]: <info> Starting VPN service 'pptp'...
May  4 18:44:50 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 7723
May  4 18:44:50 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' appeared; activating connections
May  4 18:44:50 jon-ThinkPad-T430 NetworkManager[825]: <error> [1430754290.206141] [nm-vpn-connection.c:1374] get_secrets_cb(): Failed to request VPN secrets #2: (6) No agents were available for this request.
May  4 18:44:55 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' disappeared
May  4 22:06:45 jon-ThinkPad-T430 NetworkManager[825]: <info> Starting VPN service 'pptp'...
May  4 22:06:45 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 11371
May  4 22:06:45 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' appeared; activating connections
May  4 22:06:45 jon-ThinkPad-T430 NetworkManager[825]: <error> [1430766405.913238] [nm-vpn-connection.c:1374] get_secrets_cb(): Failed to request VPN secrets #2: (6) No agents were available for this request.
May  4 22:06:51 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' disappeared
May  5 05:59:57 jon-ThinkPad-T430 NetworkManager[825]: <info> Starting VPN service 'pptp'...
May  5 05:59:57 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 12657
May  5 05:59:57 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' appeared; activating connections
May  5 05:59:57 jon-ThinkPad-T430 NetworkManager[825]: <error> [1430794797.382068] [nm-vpn-connection.c:1374] get_secrets_cb(): Failed to request VPN secrets #2: (6) No agents were available for this request.
May  5 06:00:02 jon-ThinkPad-T430 NetworkManager[825]: <info> VPN service 'pptp' disappeared