A new 3DS update has gone live which fixes feature access issues.
3DS System Update 5.1.0-11U has gone live and intends to fix problems users have experienced downloading last month’s update, 5.0.0-11U.
The previous update prevented affected users from accessing System Settings and other features.
The March update also introduced eShop improvements, including downloading software update data in the background.
Nintendo have commented on this latest update
Some users received an error during the system update and were then unable to access the System Settings, Nintendo eShop, or Game Notes. This update prevents this from occuring again.’
The update should be available to download right now