The following are some possible reasons.
Power of 5V/1.0A/5W or over is not being supplied.
In order for the system to work, it needs a constant supply of power that is 5V/1.0A/5W or over. Even if the power supply does not meet that, the system may work temporarily, but it may be unstable. Please try using a different piece of power source equipment.
The Auto-Shutdown feature is activated.
This is a feature that will automatically shut off the power. It can be set up from “Options” in the HOME Menu. If there is no input from the controller for 60 minutes, the game will be saved and the power will automatically turn off. Next time when you start the game, the unregistered Suspend Point will appear in the HOME Menu. You may continue where you left off by starting the game from this Suspend Point.
The USB cable is not fully inserted.
Check if the bundled USB cable is fully inserted into the system and the power supply equipment.
Situation Not Resolved:
If the issue persists, please contact Nintendo Consumer Support on (03) 9730-9822, between 9:00am to 5:00pm (AEST) Monday to Friday. For New Zealand consumers please call 0800 743 056.