我正在尝试从我的 Ubuntu 16.04 笔记本电脑连接 L2TP IPSec VPN 连接。每次我都面临同样的错误，因为相同的凭据可以正常工作以从任何 Windows 系统连接 VPN 服务器。
谁能指导我解决这个问题？
系统日志：
Apr 13 12:55:18 pratip-vostro-2520 NetworkManager[858]: <info> [1492068318.2586] audit: op="connection-activate" uuid="83adbec9-817f-4faf-9839-42eb41897c10" name="VPN connection 1" pid=2254 uid=1000 result="success"
Apr 13 12:55:18 pratip-vostro-2520 NetworkManager[858]: <info> [1492068318.2664] vpn-connection[0x1db45c0,83adbec9-817f-4faf-9839-42eb41897c10,"VPN connection 1",0]: Started the VPN service, PID 5561
Apr 13 12:55:18 pratip-vostro-2520 NetworkManager[858]: <info> [1492068318.2808] vpn-connection[0x1db45c0,83adbec9-817f-4faf-9839-42eb41897c10,"VPN connection 1",0]: Saw the service appear; activating connection
Apr 13 12:55:18 pratip-vostro-2520 NetworkManager[858]: <info> [1492068318.4059] vpn-connection[0x1db45c0,83adbec9-817f-4faf-9839-42eb41897c10,"VPN connection 1",0]: VPN connection: (ConnectInteractive) reply received
Apr 13 12:55:18 …