Why 4XVR still doesn't show the file thumbnails after loading for a long time?

If an individual video thumbnail is not loading, you can try to manually update the thumbnail for that video. Simply click on the three dots below the video and select "Refresh Thumbnail".

If none of the video thumbnails are loading, you can uninstall and reinstall the app. Once reinstalled, the app will rescan your video files to regenerate the thumbnails.