Instructions
Wait a few hours. The servers may be down for maintenance and will go back up soon.
Remove any objects that could interfere with your signal, such as a cell phone or metallic items.
Alter the Wii's DNS settings. In "Connection Settings," select your connection and then "Change Settings." Pick "No" for "Auto-Obtain DNS." Change the first DNS setting to 8.8.8.8 and the second to 8.8.4.4.