Lightroom photos just disappeared!

Help! All of my Lightroom photos have disappeared! I got a new Mac and copied the Lightroom library file over to the new Mac. I can see all the file structure now, but the pictures just are a black square and when I click on them it says downloading. Now, when I go to my old Mac and open Lightroom, all of my photos are gone! I then opened Lightroom Mobile and I saw all my photos for a few seconds and then they disappeared! When I log into Lightroom on the web it says I have no photos uploaded! It’s like it’s a brand new account! I had over 53,000 photos! I am devastated! I contacted adobe support and the techs asked a few questions, and then just ended my sessions. Please, please. Please help me!