Are the files on a remote location? Files will not thumbnail these by default although a setting may be changed to show them (org.pantheon.files.preferences.show-remote-thumbnails) using dconf-editor or otherwise.
Are the files on a remote location? Files will not thumbnail these by default although a setting may be changed to show them (org.pantheon. files.preferenc es.show- remote- thumbnails) using dconf-editor or otherwise.