Haven't used LR in awhile. Mac OS 10.10.5 Yosemite. When I went to install some new presets today I found that every single one of my photos in LR says "file can't be found." Have spent hours looking for photos and I can't figure this out. thanks for any help you can give.
This means that the photos (or the folders that contain them) have been moved or renamed outside of Lightroom.
You need to locate the photos on your hard disk (use the operating system's search feature) and then reconnect them in Lightroom via these instructions: Adobe Lightroom - Find moved or missing files and folders