I have LR 6 (PC version) and yesterday morning I imported photos directly from my camera (which is the method I usually use). When I tried again in the evening, it would not create previews to see any of the files. It recognizes my camera, but just doesn't show any previews photos to import. I shoot in RAW. I was able to verify it's not my camera or memory card by using a friend's computer. Hers imported everything just fine.
I also tried importing directly from my hard drive, but the same thing occurs. The center of the screen where preview thumbnails would be is empty. I can export and I can view all my other LR files (3,000 pictures in LR currently). HELP!!!
I've also tried shutting down my computer and rebooting. Nothing.
What camera? What version of Lightroom (v 6.9 is the latest)?
Did you import from the camera using the same cable on the second computer as well? Is that also a Windows machine? Can you import images from an external drive? Can you upload a screen shot of the whole import screen?