Unfortunately, it is possible that your GamePad and/or Wii U console may be defective, but have you tried removing the SD card, just in case it is in some way causing the console not to fully load past the opening screen?
Also if you have some type of external Hard Drive connected to your console, perhaps try disconnecting it to see if that helps.
But if not, probably the best thing to do is give a call to Nintendo's 1-800-255-3700 (6 am ~ 7 pm Pacific, everyday) Customer Service number, or use their webform to contact them, and one of the service representatives can determine exactly what the problem is, and if necessary, discuss repair or replacement options with you, sorry.