如题， 在NetworkManager图形界面 中没有添加tls-version-min的选项，当服务器的openssl版本比较低时， 导致nm-openvpn客户端无法 连接到服务器。

1月 14 10:24:50 steven-PC nm-openvpn[20955]: TLS error: Unsupported protocol. This typically indicates that client and server have no common TLS version enabled. This can be caused by mismatched tls-version-min and tls-version-max options on client and server. If your OpenVPN client is between v2.3.6 and v2.3.2 try adding tls-version-min 1.0 to the client configuration to use TLS 1.0+ instead of TLS 1.0 only

在shell下用sudo openvpn vpn.ovpn是可以的。