Não é possível conectar-se à VPN usando PPTP com o Ubuntu 16.04

Question

Estou tentando conectar-me a uma VPN da minha máquina Ubuntu 16.04. Fui direcionado para habilitar a opção "Usar criptografia ponto a ponto (MPPE)", assim o faço.

Quando tento me conectar, recebo uma mensagem "Falha na conexão VPN".

Quando monitoro meus logs através do comando sudo tail -f /var/log/syslog , vejo algumas mensagens relevantes:

Mar 24 15:47:59 selah-Precision-Tower-5810 NetworkManager[1420]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 5 / phase 'establish'
Mar 24 15:47:59 selah-Precision-Tower-5810 pppd[3214]: Connect: ppp0 <--> /dev/pts/19
Mar 24 15:47:59 selah-Precision-Tower-5810 NetworkManager[1420]: nm_device_get_device_type: assertion 'NM_IS_DEVICE (self)' failed
Mar 24 15:47:59 selah-Precision-Tower-5810 NetworkManager[1420]: <info>  [1490384879.0594] manager: (ppp0): new Generic device (/org/freedesktop/NetworkManager/Devices/13)
Mar 24 15:47:59 selah-Precision-Tower-5810 pptp[3244]: nm-pptp-service-3204 log[main:pptp.c:350]: The synchronous pptp option is NOT activated
Mar 24 15:47:59 selah-Precision-Tower-5810 NetworkManager[1420]: <info>  [1490384879.0649] devices added (path: /sys/devices/virtual/net/ppp0, iface: ppp0)
Mar 24 15:47:59 selah-Precision-Tower-5810 NetworkManager[1420]: <info>  [1490384879.0650] device added (path: /sys/devices/virtual/net/ppp0, iface: ppp0): no ifupdown configuration found.
Mar 24 15:48:30 selah-Precision-Tower-5810 pppd[3214]: LCP: timeout sending Config-Requests
Mar 24 15:48:30 selah-Precision-Tower-5810 NetworkManager[1420]: LCP: timeout sending Config-Requests
Mar 24 15:48:30 selah-Precision-Tower-5810 NetworkManager[1420]: ** Message: nm-pptp-ppp-plugin: (nm_phasechange): status 11 / phase 'disconnect'
Mar 24 15:48:30 selah-Precision-Tower-5810 NetworkManager[1420]: Connection terminated.
Mar 24 15:48:30 selah-Precision-Tower-5810 pppd[3214]: Connection terminated.

Alguma ideia do que está errado?

Captura de tela dos meus parâmetros de configuração: