Hi.
I've exactly the same problem .. an worst of this it's that Nintendo refuses to fix the problem (I'm out of the guarantee and they say that I've done modifications in the Wii U ... this is not exactly the case, but I did the homebrew for the Wii enclosed in the Wii U .
The Wii u is accesible trough the wii remote but , as you know, to access to the Wii U configuratiosn its mandatory to use the gamepad
Please if you've any idea of how I can solve this problem ... or what is the problem I'll appreciate.
Best Regards.