Welcome to the Community!
In new NBN order, we normally send out the modem ahead of time and some customers thought that the NBN service is already installed or activated once the parcel is received, but it isn't.
We normally send out Email or SMS notification once the service is active. If you received the notification, then you may check if the setup is correct.
Refer to our New Connection Setup Help article for guidance.
Once verified that the setup is correct and the service is still not working, please send me a PM with your TPG username or customer ID number to assist you accordingly.