I bought a new TC 2TB but it won't connect to the internet. I have the ethernet cable plugged into WAN, I've done hard resets, etc. and still nothing.

Ok so I got a brand new TC and wanted to use it as my main router. I plugged the ethernet cable into the existing router/modem/whatever and plugged into the WAN port on the TC. I set up a new network with the TC, but I got the 3 error messages in Airport Utitlity (No DNS servers, ethernet unplugged, and no internet connection). I've unplugged everything to reset it, restarted my MacBook Air, everything I could think of and my TC still won't connect to the internet. It does, however, connect with the MacBook. I've already done a backup and stored things on the TC. What do I do next?