What OS are you using?
What version of LR?
Did you move just the catalog, or did you move the pictures, too?
I moved from a Mac to a PC. The version of Lightroom I have is the 5.7.1.
I didn't touch the photos, they have always been at the same place on my HD but had to do some relocating because the HD appeared under a different letter on my PC.
Since the files are referenced by full path and name, the OS change may be coming into play here.
My initial guess is that you will need to "relocate" the upper-level folders for your images using the "find missing folder" procedures even if you don't get any "?" markers.
Thanks a lot for your answer ManiacJoe, I will try this now! I'll keep you posted.