I had the same problem when I first switched over. It turns out the modem they sent, that was supposed to be pre-configured with your account login details, was not pre-configured.
Try 192.168.1.1 and login using the usual generic for new modem, then enter your username and password to set up your Internet connection.
Welcome to the community!
I would love to help and see what happened on this. To better understand the situation kindly, PM me your account details (Username/Customer ID or Contact number Associated with the account) I will have this checked.