All of my photos in Lightroom 4 have been removed. It is now empty. How do I restore them? I have an IMAC computer.
One possibility is that you (accidentally) opened a new catalog. Go to File->Open Recent, open each catalog listed there and see if one of them is the right one.
Make sure you are opening the correct catalog. Sounds like you opened a new/empty catalog.
Go to menu /file/open recent/ and see if your catalog is listed there.
Thank you, thank you.