If it still doesn't work, there could be several reasons.
The oldest DSL systems used a LOGIN ID, which the router (or pc) had to use. If so, this would be set up inside your router. (as PPPOE) Years later, they did away with this and the routers automatically gave out the settings the devices connected to them. (DHCP method)
For AT&T customers that had PPPoE, they had 2 different methods. For Alabama, the PPPoE user ID is your full ATT email address, and the PPPoE password is your email address.
Did the ISP give you any settings, such as an assigned IP, with the new equipment?
I would suggest logging into your router, to see if PPPoE is selected as the internet connection type. Check with the ISP to see which method is currently used, with your new equipment. It may be as simple as changing the info from "PPPoE" to "DHCP/AUTOMATIC" in the router's menu. If they assigned you a fixed (static) IP, that can also be set in the same place.
There are a few different ways they do this, depending on the company. Ultimately, it's probably best to check their website or to call tech support for some help with the router.
Make sure you are able to get into the router before calling, and know your password and IP. Most Linksys routers are at
http://192.168.1.1 while many other brands are at
http://192.168.0.1 The default login is often admin with a password of admin, but it varies depending on the brand and model.
I'm not sure if I just helped you or made it sound far too confusing! heh Hopefully something above makes sense, for what they provided with the new equipment. (note: It may also be printed on the bottom of the dslmodem)