Due to stupidity on my part I inadvertently performed a factory reset.
This model does not have a dedicated WAN port.
Instead you define one of the LAN ports to act as WAN
Ausus AC68U Router & HG612 modem not working on BT Fibre 1
Router WAN won't connect to modem
I know the broadband is working because if I use my BT Smart Hub it connects and works perfectly.
I know the HG612 modem is working because if I use an external TP-Link Router it connects and works...