Thumbnail preview images

Nothing changed, but recently my Mac will no longer render preview images of icon views of Panasonic RAW files. This is most annoying as I need to see a preview in order to know which ones I actually want to edit or dispose of... My workflow has ceased to exist because of this. I know others have this issue and suggest to just get a preview app, but that doesn't solve the initial problem... Why should I have to purchase yet another app to see what the OS should already do, and DID do until recently? As I stated, NOTHING changed. no updates, no RAW file change. It just stopped working out of the blue...