If you attempt to start a stream and see a notification in the log indicating "The server is not available," this can often be fixed by manually selecting your network under Stream > Advanced Settings.
In the Stream tab, select Advanced Settings to expand the panel.
Under Specify Network, select your network instead of "Use default network."
Note that if you are streaming to multiple destinations, you may need to do this for each provider to which you are streaming.
Once this is done, select the Go Live button again to start your stream.