Server failing to fetch server variables

We have been trying to set a server up, we complete installation but when someone connects, we get this message in panel:

[ citizen-server-impl] Server list query returned an error: System.Threading.Tasks.TaskCanceledException: A task was canceled. ← System.TimeoutException: A task was canceled. ← System.Threading.Tasks.TaskCanceledException: The request was canceled due to the configured HttpClient.Timeout of 30 seconds elapsing.