The first version of Camera Raw to support the D810 was 8.6. However, 8.6 will not work with CS4. So, you options are to either upgrade CS4 to something newer (CS6 supports up to Camera Raw 9.1.1, so that would be the minimum version you'd need), or use the free DNG Converter to convert your files to DNG before importing.
More info on this issue, along with info on the DNG Converter, can be found here:
Here is how to Open NEF Files in Photoshop:
- Download the Adobe DNG Converter: This is a free utility that is available for both Windows and OS X. You can download it for free from here.
- Once you've finished downloading it, run the setup program to install the converter on your computer.
- Run the converter program. Once the installation has completed, run the Adobe DNG Converter program to open the conversion interface.
- Select the files you want to convert. Click the Select Folder... button in the first section to choose which images you want to convert.
- You can only select folders containing images, not single images.
- Select where you want to save the converted images. By default, they will be saved to the same location that the original images are stored.
- Set the image naming settings. In the third section, you can set how you want the converted images to be named. By default, they will keep the original file name but add the .dng extension.
- Set your compatibility preferences. Most users can leave these at their default settings, but if you're trying to convert an image so that it opens in an older version of Adobe Photoshop, click the Change Preferences... button and select the version you use from the "Compatibility" drop-down menu.
- If you want to embed the original NEF file in the DNG file, you can select this from the Preferences menu. This will result in a larger DNG file, but will allow you to extract the NEF file again later if you need it.
- Start converting. Once your settings are correct, click the Convert button to begin converting the files. This may take a while, especially if you are converting a lot of files at once.
For more assistant support please refer to Nikon d810 Manual.