Thanks for the update @angel1234.
We tested the line and it shows that the NBN NTD box is down.
Are you able to check the light status of it? And please check the cables and make sure that they are properly connected to the power and coaxial outlet.
That's why I was confused and advised to check a coaxial wall socket since you are using an ARRIS NBN NTD box.
The said device is for NBN HFC technology only, if you are under the NBN FTTP service, a different NTD box is needed.
Please check your house if you can locate it. Refer to the picture on the NBN FTTP setup article that we've created.
The ARRIS NBN NTD box is not for the NBN FTTP service.
Check the type of NTD you should see on your house.
It is a white box that is mounted to your wall and the case has an NBN Co label.
Are you able to search for the NBN NTD box?