If your LeapPad does not appear to charge when plugged into the wall adapter, you will first want to verify whether the issue is with the power adapter or the LeapPad.

When plugged in and charging, the charging indicator light on the LeapPad should glow yellow/orange.  On the LeapPad Platinum and LeapPad Ultra, the charging indicator light is right next to the USB port.  On the LeapPad3 the charging indicator light is around the corner from the USB port:

If the charging indicator light does not glow when the LeapPad is plugged into the wall adapter, find the USB cable that came with the LeapPad and use the USB cable to connect the LeapPad to a powered USB port on your computer while the computer is turned on.  If the light glows when plugged into your computer, this will verify the power adapter is not working.  If still within the one year warranty period, contact LeapFrog support for a replacement adapter at no charge.  If outside warranty, power adapters are available as a separate accessory at most retailers that carry LeapFrog product.

Please note, checking the charging using the USB cord is for testing only.  The LeapPad charges very slowly when connected to a computer.  It should be charged with a working wall adapter for proper charging performance.