Calibre keep deleting book

I'm not on a mobile device, so I apologize if I'm in the wrong area. But I think others have this problem, too.

Each time I add a book, it appears and now ALL the books disappear. I try putting them all back in and then after I leave and return, all the books are gone again.

What am I doing wrong? I am using Windows 10 and the latest iteration of Calibre.