8.7 will open all preceding cameras, as well, so that’s not the problem.
It is likely that your NEFs were touched by obsolete Nikon software like Nikon Transfer or View NX and this corrupts the NEFs slightly so that Adobe software cannot use them.
You can test for this scenario by not using any Nikon software with some new NEFs, instead using Bridge or native Mac/PC software to transfer and view the images prior to opening in PS/ACR.
If the files are important, you can reverse the corruption using the following utility:
How are you transferring the photos from the camera to the computer?
If you're using Nikon software then older versions are known to make Raw files unreadable to Adobe software.
If this is the case, try eliminating Nikon software from your workflow and downloading via a card reader.