Photoshop v27.8.0 no longer displays thumbnails, only a generic icon

When working with images (png., jpg., tiff etc) I no longer see thumbnails of the images in the directory I am working in. If I open the image and do some work on it and then do a Save as, move to the directory I want to save in I still do not see any thumbnails of the images in the directory, only generic icons. I have not changed any settings in Photoshop so don’t know what has happened.