@Chrischiang @Shaggi
1st, try AGL's internet phone tech line support,
If you want to see something tangible immediately then try the below.
https://telcostatus.agl.com.au
Failing that then have a look see here.
https://www.nbnco.com.au/support/network-status
If everything looks good there then try the tips here.
https://www.agl.com.au/help-support/internet-mobile/troubleshooting-and-outages/internet-troubleshoo...
If still no luck then I would recommend ringing AGL direct again to see what can be done, This depends on a few factors IE: NBN issue or Southern Phone issue.
My post takes into consideration that the modem settings have not been dropped as I have commonly seen in the past.
Regards
John