You can login but cannot access all the maps without it.You will crash or become stuck.Please update.
1. You can go download it here and put the files into the specific folders http://neverwintervault.org/cep
2. You can subscribe to CEP through steam . It will download automatically for you. You may have to restart the game to trigger the download.
3. Accept the download privided by the nwsync system that appears through the game client when you try to login .
The CEP I believe now is about 4gb.