Xbox Live is currently down for most Xbox One users due to the fact that a bunch of script kiddies are DDOSing the Xbox Live servers. I feel so sorry for anyone who received a console for xmas.. It doesn't matter if you got a PS4 or Xbox One, you won't be online for a little while.
Here's the official info from xbox.com:
Xbox Live Core Services Limited
Affected platforms: Xbox One
Affected services: Signing into Xbox Live
12/25/2014 9:02:31 PM CST: Xbox members, are you experiencing issues when attempting to sign in? We’re aware of this issue, and we’re working to find a fix ASAP! We appreciate your patience in the meantime, and we encourage you to retry signing in when you get a chance. We’ll update you as soon as we know more.
Xbox Live Network Status:
http://support.xbox.com/xbox-live-status