The North American Hearthstone servers are currently down. You will have to wait a bit before trying to open your new Whispers Of The Old Gods cards. Blizzard is currently working on it according to their Customer Service Twitter.
[#Hearthstone] We're investigating an issue affecting our authentication servers, which may result in failed or slow login attempts.
— BlizzardCS (@BlizzardCS) April 26, 2016
The server maintanence was supposed to be done by 1:30 p.m. EST, but something may have gone wrong. We will update this post as information comes out. In the meantime, try not to panic. Your packs will still be waiting for you once the authentication problem gets fixed.
EDIT: The servers sre starting to let players in little by little, but the servers are looking stable.
