Thanks for raising this with us @seongmini.
We checked the photo you attached and noticed that it says the WAN port is unplugged.
Are you able to check and make sure that the Ethernet cable connecting the modem/router to the NBN NTD box is firmly connected?
Have you tried rebooting both devices as well? If not, please try it first.
If it's still not working and the service is not affected by an outage, please send me a PM with your TPG username or customer ID number to assist you accordingly.