From Nikon:
Support Article
My COOLPIX camera battery will not charge - Firmware Updates available
How to identify the camera battery not charging
The cameras listed below are all designed to charge the battery in-camera by connecting an AC adapter to the cameras USB connector. If the battery is fully exhausted due to a long period of inactivity, sometimes the battery can fail to charge. With the AC adapter connected to the cameras USB connector the battery charge lamp will flash green if charging is in progress. If charging is not possible the battery charge lamp will not light at all.
The battery charge lamp is usually located on the back of the camera indicated with a charge/flash symbol.
Camera Firmware Updates available
Nikon have released camera Firmware Updates for the following affected COOLPIX cameras. We recommend performing the update as soon as possible to avoid this problem should your camera not be used for long periods.
Important Note
Make sure the battery is fully charged before perfoming a Firmware Update, alternatively power the camera from an AC adapter unit. If you perform the update with a battery which is not fully charged the camera may stop working during update which will cause further problems.
My camera has no power, I can't update the Firmware!
If your camera will not charge the battery, try the following workarounds which may recover the situation enough to allow the battery to continue charging.
If these measures fail to charge the camera battery, contact the Nikon Support Centre for further advice.