我正在尝试连接到工作 VPN，但每次尝试连接时都会失败。VPN 已在网络管理器 UI 中配置，连接也从那里开始。我检查了系统日志并看到以下内容：
Jan 28 08:29:09 cwlt NetworkManager[751]: <info> Starting VPN service 'pptp'...
Jan 28 08:29:09 cwlt NetworkManager[751]: <info> VPN service 'pptp' started (org.freedesktop.NetworkManager.pptp), PID 6383
Jan 28 08:29:09 cwlt NetworkManager[751]: <info> VPN service 'pptp' appeared; activating connections
Jan 28 08:29:09 cwlt NetworkManager[751]: <info> VPN plugin state changed: starting (3)
Jan 28 08:29:09 cwlt NetworkManager[751]: <info> VPN connection 'VPN' (Connect) reply received.
Jan 28 08:29:09 cwlt pppd[6387]: Plugin /usr/lib/pppd/2.4.5/nm-pptp-pppd-plugin.so loaded.
Jan 28 08:29:09 cwlt pppd[6387]: pppd 2.4.5 started …