在导入 ovpn 配置文件后，我试图通过网络管理器插件 (network-manager-openvpn) 连接到我的 OpenVPN 服务器。但是，我收到超时错误：
$ grep VPN /var/log/syslog
Oct 1 11:56:05 packer NetworkManager[997]: <info> Starting VPN service 'openvpn'...
Oct 1 11:56:05 packer NetworkManager[997]: <info> VPN service 'openvpn' started (org.freedesktop.NetworkManager.openvpn), PID 4700
Oct 1 11:56:05 packer NetworkManager[997]: <info> VPN service 'openvpn' appeared; activating connections
Oct 1 11:56:05 packer NetworkManager[997]: <info> VPN plugin state changed: starting (3)
Oct 1 11:56:05 packer NetworkManager[997]: <info> VPN connection 'vpnt' (Connect) reply received.
Oct 1 11:56:05 packer nm-openvpn[4703]: OpenVPN 2.3.2 x86_64-pc-linux-gnu [SSL (OpenSSL)] …