The Nintendo 3DS system was unable to connect to the network for an unknown reason.
Did this connection used to work but has suddenly stopped? "Power cycle" your router and modem. To do this, unplug both the modem and the router from the power outlet. Wait a few minutes, and plug the modem back in. Wait a couple of minutes for the modem to initialize, and then plug in the router. Try to connect the Wii, Nintendo DS, or Nintendo 3DS online and test for proper response.
Set up a manual connection file. Click here for step-by-step instructions for manually assigning an IP address and DNS server to your Nintendo 3DS system.