You need at least Lightroom 5.6, what is the exact version number of Lightroom you are using?
What happens when you try to import? Describe in detail. If there is an error message, please quote the exact complete unedited word-for-word error message.
Thank you for your swift reply.
I am using LR 5.7, camera raw 8.7.
While importing the previews appear with a message " Previews unavailable for this file".
the message that appears after attempting import says : " files are not recognized by the raw format in LR (1218).
I use an IMac Mac OS X Lion 10.7.5 (11G63).
This usually implies that you have used Nikon software on these photos, which changes the header in the files, making them unreadable to Adobe software.
Try importing the photos directly from the camera card into Lightroom, with no Nikon software used in the process.
Thank you again for your reply. Yes is true. I have downloaded the files into the archive with Nikon transfer. I will try as you recommend . If I have any trouble I will let you know. I will only be able to do this once I get back from work, , at night.
Using Nikon Transfer is not necessary, but if you are going to use it, make sure you are using the most recent version of the software. It is a well known problem that using old versions of Nikon Transfer on new format NEF files from new camera models will corrupt the NEF files during transport.
Thank you guys! Job done!