Hi @Scoopy18 .
From the manual, Nighthawk AX5 Model RAX43.
Does your internet connection require a login? YES
Internet Service Provider menu: PPPoE
Login: username with @tpg.com.au on end
Password: account password
For IP address and DNS address, select Get dynamically from ISP.
You also need to set VLAN ID=2 for internet access. The manual has instructions to "Set up a bridge for a port group or VLAN tag group". I'm unsure of which set of instructions to use here. Whichever one, you connect all ethernet ports and wireless to the group.