Importing images into Lightroom Classic

I use a Nikon D810 camera, I shoot nef raw mode this has only happened when I import the raw images into my PC using a Sandisc Extreme USB 2.0 reader and attached to the PC via a cable into a USB port on the PC. When the import is finished I get a message saying that the image file showing on the PC, that the file is not recognized this can happen to all of them or just a few images. I would appreciate any help as to what is causing this problem I have. Thanking You John Steadman.

Hard to say. Until recently I used to always import directly from my Canon 5D4 camera. However, my more recent Sony has a connector which appears to be much less robust so I have now started to use a cheap card reader but no issues.
Have you tried importing directly from the camera? Have you tried another card?
Dave
Have you tried importing directly from the camera? Have you tried another card?
Dave

I suspect this may have something to do with the 'Preferences' you have chosen. There is a very useful guide for this here
https://helpx.adobe.com/lightroom-classic/help/raw-defaults.html
and if that doesn't help then maybe the Adobe Forum could.
https://helpx.adobe.com/lightroom-classic/help/raw-defaults.html
and if that doesn't help then maybe the Adobe Forum could.