"Unsupported or damaged" usually means your camera's RAW photos are not supported by the version of Lightroom you have installed.
So, what camera is it, and what version of Lightroom?
"Could not be read" is usually a permissions problem where you do not have write permission to the destination folder, where the photos are supposed to be copied into.
It is Lightroom 5.7. and
I don’t understand the “write permission”. They’re my photos.
What are the flashing bars?
Have you used any Nikon software on these photos at any point in your workflow?
Was the one photo that "could not be read" by any chance a JPG and not a RAW?
It is possible that the photos are indeed damaged if you are getting that message. You might want to try importing them again, using different hardware (ie if you were using a card reader, try the direct cable to the camera instead)
Permissions are something that you set in your operating system. Go to your favorite search engine and type in Change Permissions Mac
I successfully imported most about 1/2 of the images, by
only editing my best, most important images.
I don’t care about the rest.
I’m trying to figure out what happened to avoid this in the future,
because I couldn’t get all the images & I don’t want that to happen again.
I was using a direct cable to the camera
Do you think my memory card is wonky?
It could be the card, or it could be the cable, or it could be the USB port or the port where it connects to the camera. That's why you need to try using other hardware to perform the transfer to see if you can isolate the cause of the problem.
Never use a cable directly to your camera! By doing this, the power to the card in the camera comes from the camera battery. If the battery runs low during the import, the images can easily get corrupted. Remove the card from the camera and insert it in the SD slot on your computer, or get a reliable card reader.
Can you recommend a reliable card reader?