Get online support
Are you on FTTP? If so, what lights are on on your NBN box? If Optical is green, the problem is almost certainly at your end (possibly router). BTW, IF you are on FTTP, the modem function is now in the NBN box; your own device is a router.
Before performing any troubleshooting, we advise customers to check if their service is affected by an outage.
If not, please send us a private message with your account details and we'll see how can we help.
BasilDV