I had a similar problem with a mifi device. In the end I connected using a cable (ethernet for you, mine was via USB - a detail but not really relevant!).
If you connect by ethernet, you should be able to conect to the router and use its admin password to access the settings. Then you can check whether the wifi password is the same as is printed on the label! If not, then you can change it to something you recognise.
By the way, just to double check, I hope you've been trying to connect to you new router over wifi, i hope you entered the wifi passwordn and not the admin password of your TT account password, something that is easy to do, even for the most experienced person