I'm scratching my head on this.
When I got home from holidays I fired up my Wii U to download SMG, but it refused to connect to the internet.
Rebooting the Wii U and router multiple times did not help.
The Wii U can see all wifi networks and recognizes the encryption used, but attempting to connect to mine, my phone, and any other gets the error of "no WIfi networks found." despite being able to see all networks in the vicinity just two screens ago. I verified that I'm typing the correct password
Eventually I got it working, but only for twenty minutes after which it refused to connect again.
I reset my router to factory defaults and set up a completely different network, which made no difference.
I suspect my wifi card is gone. I'm away for a little longer but I left my Wii U unplugged and ordered a USB ethernet adapter.
Is there anything else I can do? I don't want to call Nintendo as I have a massive library on my hard drive and upgraded the Wii U's gamepad battery.