This is ADSL connection? Is the router from TPG? Is it a TPLink TD-W9970?
When you turn the router on, the second light (DSL) should flash while it negotiates with the exchange. If the light is off or flashes forever, there could be a line fault. TPG will arrange with Telstra to fix this.
If DSL light is on, you need to check the settings provided by TPG.
Is there another telephone outlet you can check?
Do you have a landline telephone service? Does it get a dial tone?
Before attempting the troubleshooting steps, we recommend that you do the following below.
If you are still unable to connect to the Internet, you can proceed with the troubleshooting steps indicated on this link: https://www.tpg.com.au/support/problems_connect_internet.php
In your case, we've tested the line and there's a possible fault within the copper line. We've raised the case with our Engineering team and an assigned Engineer will be in touch with you via SMS or phone call within 24 to 48 hours.