This error may occur when you attempt to connect to a GN4 server, while the IIS service is stopped. The reasons may be:

1.The upgrade procedure is running on the GN4 server and therefore the IIS is temporarily stopped. The upgrade procedure may take about 30 minutes.

2.The IIS on the server is stopped.

3.The server is not accessible from the outside.

4.The server is not started.

To correct this error

1.Wait about 15 minutes and then retry. If it still not responds, retry in intervals of 5 minutes for the next 15 minutes. If the server still does not respond, then check the server status.

2.Check the IIS status and restart it.

3.Check the firewall settings.

4.Restart the server.