Nintendo is taking the eShop down for a 12-hour period today for a round of emergency maintenance. The digital shop for both Wii U and 3DS will be down from 1 PM to 1 AM Pacific, in an effort to fix some lingering issues from its Christmas Day outage.
A post from Nintendo's Facebook page reads:
We sincerely apologize for the connection problems in the Nintendo eShop. We understand this is taking longer than expected, but we can assure you that providing a solution is our top priority. We are determined to make sure everyone can enjoy all that Wii U and Nintendo 3DS have to offer. In an effort to manage the high volume of traffic and ultimately improve your experience, we are temporarily taking the Nintendo eShop services offline between the hours of 4 p.m. - 4 a.m. ET. Thank you so much for your continued patience. We will keep you updated.
The eShop originally went down on Christmas Day due to high online traffic, which can be attributed to the influx of new Wii U and 3DS owners. Of those new owners, many of them also had digital titles (such as The Legend of Zelda: Wind Waker HD) to redeem through the eShop, adding further to the traffic volume.