title: Thumbnail preview not showing on mac OS Catalina
body: <p>I upgraded to Catalina, thumbnail preview stopped working on my desktop.
  I tried everything that I know, &quot;Show icon preview&quot; is ticked, Preview app is applied to open all kinds of images, but still just the generic icons appears. This is very frustrating, since I am working with images and video files, that I need quick access to.
  Hope to someone help me with this.</p>