I'm using Acrobat Pro DC on Windows 10. Until today, my pdf files would show the Adobe Icon, but now they are showing a thumbnail of the first page of the document (which, to me, makes everything more confusing). I checked preferences > general > enable PDF thumbnail previews in Windows Explorer and the box was already unchecked. I checked it and unchecked it again, then restarted my computer to see if the icons were refreshed and they kept showing the thumbnail instead of the adobe icon. I tried opening them in Acrobat reader, but it also didn't work. Does anyone have any idea of what I could do?