Wii U will not turn on
Try a different power source
If your Wii U console is not switching on, try connecting your console to a different outlet. Be sure not use any extension cords or surge protectors.
Reset the AC Adapter
Unplug and remove any accessories: games, controllers, memory cards, SD cards, connection cables, the AC Adapter and the Sensor Bar from your Wii U. Then let the system rest for at least 90 seconds.
It is important that you let it rest for the full 90 seconds, as it will not reset if you do not wait.
While you wait, check that the AC Adapter is a licensed accessory by verifying the model number (WUP-002). If your AC Adapter is unlicensed, do not use it as it may cause damage to your Wii U.
You should also check your AC Adapter for any signs of physical damage, such as frayed cords and cracks.
After 90 seconds has passed, plug your AC Adapter back in and attempt to switch your Wii U console on.