Reports are coming from some Nikon camera owners that after installing a firmware update designed to improve the features for a specific battery pack - the EN-EL14a - their cameras no longer accepted third-party versions of the battery.
The firmware update was for the Nikon D5200, D5200, D3200, D3100 and Coolpix P7700 and there doesn't seem to be any way to roll back to a former version. Since installing it, readers of Nikon Rumors have emailed the site to say their non-branded EN-EL14 batteries no longer function. In addition, Nikon's own batteries no longer work in third-party pistol grips for those models (where applicable).
READ: Nikon D5200 review
Nothing about this alteration in compatibility was noted in Nikon's change log and, at present, Nikon hasn't commented. For the foreseeable future, if you own any of the affected cameras and run them on third-party power packs, do not upgrade the firmware.
It could be a very expensive process to replace any batteries or spares with Nikon's own authorised versions. It generally charges around £40 for a compatible battery, while you can pick up third-party equivalents, including one from Duracall, for less than half that price.