@Pabbs74 Have look here https://www.optus.com.au/about/network/service-status
Click on Outages then Fixed Outages enter you details and see if there is a reported outage.
The NBN also has an Outage page
If there are no reported outages here are some troubleshooting tips
If there are no reported outages and the troubleshooting does not fix your issue you can message Optus Support via the My Optus app. You can also try calling 133937 ignore the prompt to press 1 and wait for the options. I have read the wait on the phone can be long.