I had seen this issue before on my 4K Apple TV. My library of almost 3000 movies/TV shows was empty for over 6 months and then was magically fixed one day. Right after I updated to Catalina, the library is now empty again. I logged a support ticket with Apple over a week ago and they have no clue what is causing the issue. My Apple TV 4K has the blank library again too. I tried logging into a different account and am able to see a library so not sure what the issue could be. My library still shows fine in the the Itunes Movies and TV apps.