ACR (Adobe Camera Raw) versions are specific to different versions of Photoshop.
According to this link on Adobe's website regarding supported cameras
The Nikon 5200 required at least ACR 7.3, but you need Photoshop CS6 to run ACR 7.3 It won't work with older versions of Photoshop.
You can download the latest version of DNG Converter and convert your 5200 files to DNGs that can then be opened in earlier versions of Photoshop.
Here is the link for Windows: Adobe - Adobe Camera Raw and DNG Converter : For Windows : Adobe DNG Converter 8.4
Here is the link for Mac: Adobe - Adobe Camera Raw and DNG Converter : For Macintosh
The DNG Converter only works on folders of files, don't try to select an individual file to convert, Choose the FOLDER.
I have ACR 8.5 in photoshop CC and CS6, but Nikon d5200 raw files will still not be read in photoshop. This seems to be a known issue with Adobe software. I will see if the conversion to DNG files will work. Thanks for trying.
DNG 8.5 did not work either to change raw files from the Nikon D5200 camera. The problem seems to be in using Nikon Transfer software to transfer raw files to the computer. None of the raw files will open in Adobe software (but will still open in Nikon NX software) when Nikon Transfer is used. Apparently Nikon Transfer screws up the raw file so Adobe programs cannot recognize the file.
When I plug the SD card directly into my Mac Pro and drag all files directly onto the computer without using Nikon Transfer then the Nikon raw files can be read in Photoshop CC so I guess that I solved the problem without any help from Adobe or Nikon.
There may be many thousands of Nikon users who have this problem!
Nikon Transfer has been discussed before. The general advice is to avoid its use.