Lightroom Not Showing External Hard Drive/Image Files.

Hello all, 

I am a college student currently enrolled in a photography class. When I began this semester, my external hard drive, where my lightroom catalog lives, everything worked fine. I've had this drive for just about five years now with no issue at all. My drive is set up to work on both PC and Macs. But when this school semester began, I plugged it into our school, Mac desktops. At first, everything was fine. Then when I would go back and forth from my Mac laptop to the school's Macs, my lightroom began having troubles. When I would open Lightroom Classic, sometimes my files of all of my images would come up with the little question marks, indicating that every single image could not be found. So Logically, I would go in and find one image. When I did this, it would find all of my other folders, but clear the folder, I found the one image to zero. I ended up having to reupload that now empty folder again and call it something else because everything on the back end (in my camera files) were still there. Nothing has ever been permanently deleted off the drive, it just disappears from lightroom. So now, I open Lightroom Classic, and it is not showing my hard drive at all. All of my folders are gone. It just shows the hard drive of the computer. But again,everything on the back end of my catalog is there on my hard drive. All of my raw images and data. Lightroom just isn't allowing it to show up in the program. I really don't know what's happening or what to do. Any help would be much appreciated.