Welcome to the community!
For newly installed NBN service, we did an article that you may find helpful.
In the event that you successfully set up the NBN service and still not working you may check if there is an ongoing outage affecting the service. See this link for reference How to Check for NBN Network Outage.
In this particular case, we can see that the install for NBN has been completed and the modem/router requires to be manually configured to work. We've seen that the issue has been escalated to our Engineering Team for further investigation and handling. Updates will be provided when it becomes available via SMS or Phone call.