Nighthawk AX1800 mesh wifi 6 MR60 cannot connect internet

Hi I am in Melbourne Australia and I have got a big issue of my Nighthawk AX1800 mesh wifi 6 system, and the router is MR60. My modem is a Huawei HG659, which has router function. The issue is I just cannot connect it to internet. I tried different ways under guidance of technical support staff, I filled in the PPPoE number, re-set the router for several times, but ever time when we run the Setup Wizard, it asks for the fixed IP settings. I called the internet supplier (DoDo in Australia) and they told me it's not their issue, as the router should automatically adjust itself to suit the modem. Can anyone tell me what can I do now? Thanks a lot.

firmware version is V1.0.6.102_2.0.45