Welcome to the Community!
I'm sorry about the service disruption. Based on our records, there was a maintenance done by NBNCo which started at 7AM AEST today and should have ended by 3PM AEST today as well. That being said, it appears that your modem regained the connection as early as 8:07AM AEST and is still connected to the server. Let me know if you're still having trouble connecting so we can look into it further.