Welcome to the community!
If you're having issues with 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 you may perform basic troubleshooting, we did an article that you may find helpful see this link below.
For ADSL2+,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 this particular case, we've seen that the configuration of the modem/router has been reconfigured which fixed the issue. Should you need further assistance, feel free to search community for help or chat with us at https://www.tpg.com.au/support/contact/ and we'd be glad to assist you.