Welcome to the community!
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.
In this particular case, we can see that the issue with the service has been raised to our Engineering Team and escalated to NBN Co. Updates will be provided when it becomes available via SMS or phone call.