Welcome to TPG Community!
Please go to http://192.168.1.1 and refer to the log in details that can be found on the box or at back of your Sagemcom modem. You can go to the Basic Tab as this where you can check the status of each Wi-Fi band and configure their SSID and password. Our Team is already working on a new firmware to fix USB Type C function, but there's no ETA as of the moment. Once it is available, we'll provide an update in the Community.
Are you still not able to login to your modem interface?
Could you provide a picture of the back and bottom part of the modem/router for us to check if there's any label or sticker on it?
The user ID is admin, but the password is different and has a label of Web login.