> Missing Quick Look previews
Why have some Quick Look previews stopped working in macOS 15 (Sequoia)?
Apps with custom file types will show generic icons in Sequoia if their Quick Look support hasn’t been updated.
Image rights: Apple Inc.
This is because of a change in how third–party apps create Quick Look thumbnails, shown in Finder windows, and Previews that open in their floating window. Prior to macOS 10 (Catalina), these were made by using special qlgenerators, usually installed in the QuickLook folder in either the main Library folder, or its equivalent in the Library of your Home folder.