Welcome to TPG Community!
Based on an account located, the service has been affected by an unplanned maintenance yesterday but all has already been resolved now. We apologise for the inconvenience caused.
Should you still require assistance, please don't hesitate to let us know.
We apologise for the inconvenience this has caused you, @zhaoyang1011.
As per checking, NBN Co. has identified a fault on the network yesterday and has engaged field services to rectify the issue. They have replaced some network hardware and your service should be working now.
Feel free to drop us a message should you need any assistance. Thank you.
I've checked the status of your service and your modem shows connected and has an internet access for more than 2 days now.
Were you able to check if you are connecting to the correct Wi-Fi? Is housemate's mobile phone connected to the home Wi-Fi or is using mobile data? Are you able to perhaps ask how is he/she able to connect the device(s)?
Please try to connect your devices using the Wi-Fi details indicated on the sticker at the back of the modem.
You may try checking this Community link for other helpful information: Wi-Fi troubleshooting steps - No Internet/Connection
Should you still require assistance, please let us know of your best contact time & number via private message so we can organise a call back to be made from our Technical Team for assistance.