Several readers emailed me with reports that their third party EN-EL14 batteries no longer work after the last firmware update for the D3100, D3200, D5100, D5200 and P7700 cameras. It also makes it impossible to use Nikon batteries in third party battery grips. Of course Nikon did not mention anything about that in the change log. I am not aware of any way to revert a firmware update and Nikon does not provide download links on the their website for old firmware updates.
Update #1: some third party batteries work even after the firmware update.
Update #2: few readers have successfully downgraded the camera firmware to the previous version without any issues. Older firmware updates can be found on Nikon USA support website. For direct links, check the posts under the firmware tag on NikonRumors. Please not that you can brick your camera by downgrading the firmware.