Unable to connect to the Nintendo eShop. Can also occur when trying to access other online applications.
Likely the result of your connection timing out, most often caused by wireless interference.
What to do:
Check for wireless interference.
Wireless interference between your Wii U and wireless router may be causing the download to time-out. As an easy solution, try moving the Wii U into the same room as your wireless router during the update, and then moving the Wii U back once the update is complete. If you are unable to do this, try our more extensive wireless interference troubleshooting. [How to]
Manually enter a network IP address and DNS into the Wii U.
Entering your network settings into your Wii U console can resolve issues that are related to connecting to your router. [How to]
Still Not Resolved:
If the issue persists, please contact us at 1-800-255-3700. Specially trained representatives will be available to assist you, 6:00am - 7:00pm (PST), seven days a week.