Welcome to the Community!
Thank you for reaching out to us. I used your community details to check your account to find out what's going on.
I was able to find that NBNCo noted a maintenance work done between 11PM of February 26th to 6AM of February 27th. Although it should have been up after 6AM yesterday, it's possible that the disruption may have continued beyond the time they've set.
I can see that your service is already back up and running at this time. Your modem showed connected to the server for more than 22 hours already.
If you're still having trouble, please don't hesitate to contact us.