The D7100 has been supported since Lightroom 4.4. But the D7200 was not supported until Lightroom 6. What version of Lightroom are you using?
Hi Sorry for delay I am using light room 5 Kind regards Frank
If you have simply added some D7200 NEF files that you want to work with, you could download the latest DNG converter and create DNG files that you could use with the Lightroom you have installed. If you have upgraded to a D7200, and want to work with the native NEF files, it will be necessary for you to upgrade your software. If you need a link to the DNG converter, please specify your operating system.