Been using LR 6.0 with camera raw 9.0, and latest Nikon codec from 2017 in a win 7 workstation, 64 bit. No issues importing old D5000 photos in raw or jpg files. A typical photo is named DSC_0001.NEF. Tried importing new photos with same file name format from D5600 Camera in raw and jpg format and get error as follows: "The files are not recognized by the raw format support in Lightroom. (98)" and then it lists all the file names of the raw photo files. The camera also took jpg versions of the same photos in the same directory and it did not show the Jpgs on the rejected photo error message or in the list of imported photos (a null set). The old D5000 photos are approx 12mp, the new D5600 photos are approx 24mp.
The first import rejection was when I tried a memory card direct import into LR which gave the error message. Then I imported the same photos into a windows directory off the same memory card and was able to view them fine in either NEF or jpg format with the windows explorer viewer. I then told LR to import all of the photos from that windows directory and got the exact same error message.
I'd hate to purchase a new lightroom by the month simpl;y to gain access to my family photos ( 60,000).