I am having trouble rendering 1:1 previews. It has worked amazingly well in the past, but upon uploading a recent shoot NONE of my images have previews and of course, it is now running slow when trying to work on images. I have tried rebooting my system, have actually restored my computer to a previous checkpoint, reinstalled lightroom. Nothing is working. :-/
If you are using Lightroom 6/ CC 2015, please turn off the Graphics Processor from the Lightroom preferences.
Go to Lightroom Preferences from the Edit menu
Click on Performance tab
Uncheck the Graphics Processor