I am using LR 2015.2.1 in MBP retina 2015 with El Capitan. I am trying to import RAW pictures from my Canon 6D. The import screen works well but after you press the import button and the application comes back to the main screen, the "copy and import photos" progress bar will never increase and no photo is imported. I tried Lightroom 2015.2.1 import freeze/ crash/ hang but it won't help.
Please try the below steps to fix the Issue.
Turn off the GPU
Click on Lightroom on the Finder menu
Go to Preferences
Click on the Performance tab
Uncheck the GPU
Then, Go to the General tab
Uncheck the Option "Show Add Photo Screen"
Restart the Lightroom and the Import Again.
Let us know if it helps.
Now if in case you are getting a black thumbnails after import, please refer the link: Thumbnails display black in Lightroom CC 2015.2/6.2