When this error occurs, the logging messages from ngutil look like this:
09:50:35.704 D Connection closed. 09:50:35.704 D IoClose completed, status 0x5023 09:51:19.633 D LPRPCTransportSSPI::Connect() FAILED 09:51:19.633 I No logon server was detected on the appliance. [220.127.116.11] 09:51:20.367 E RasCustomDial completed with errors. Error 0x000004D0: The network location cannot be reached. For information about network troubleshooting, see Windows Help.
For appliances setup with self-signed certificate, we need to use the following command to ignore certificate warnings: