The error you received indicates that your network NAT type is Moderate or Strict, and this is preventing you from connecting with other users. (If you're uncertain what NAT is, you may find our information on helpful.) Issues related to NAT type are likely due to your network firewall settings. These issues can often be resolved by enabling UPnP on your router, placing your system into your router's DMZ, or forwarding ports within your router.

Are you using a public network, such as at a college dorm, hotel, etc? In many situations, users experiencing NAT related issues caused by these networks cannot resolve them on their own. If you're experiencing an issue related to your NAT type, please contact the network's administrator for additional assistance and to find out if the network will work for you.

Next step

Ready to start troubleshooting? Learn more about NAT Related Troubleshooting on Wii U step 1.