Can't see JPG and PNG previews needed to select files (Win10)

Hi - while I can see JPG and PNG in my PC's Explorer, I cannot see previews when I try to select a file when in Photoshop.

I used to be able to see them, but now, no previews at all. I've looked all over for a setting in Preferences, but couldn't find one. I do have previews set in Explorer, so I know that they are there. In order to retrieve files today, I need to do so from Explorer and not inside Photoshop.