Hi @e11eventy8 . Is the Asus replacing a working router, or are you using Asus on a new connection?
What lights are lit on the NBN box?
The Power, Optical and Alarm should be green.
You should have an email from TPG indicating which UNI-D port should be used.
When connected, the UNI-D light should be orange indicating a gigabit router is connected-Asus.
Having set PPPoE, are WAN and NAT enabled? VLAN ID is not used on FTTP connection.
Go to Advanced Settings, System Log. The General log might indicate the problem.