Welcome to the Community!
For customers experiencing any issues with their NBN service, we recommend the best thing to do first is check if there's an outage on the NBN network.
We have created this article that can guide you on How to Check for NBN Network Outage
If there are no known outages in your area, customers can proceed with the troubleshooting steps indicated on this article :Troubleshooting No Dial Tone - TPG Home Phone/Voice Service
In your case, we've detected a usage within your home phone service that indicates that it's already working.
Feel free to search Community for help with your issue, or contact us and we'd be glad to assist you.