Lightroom version CC 2015.12 [ 1125239 ]: I am using Windows 10. After the last update all my photos appear as gray blocks in my library. It does not have exclamation marks so it is not that the photos have been moved. I can see the photo in the develop tool. The same situation happened maybe a year ago and in the end - with a live chat and Adobe support they took control of my PC and fixed it. Unfortuantely I do not know how they did it then.