The specification page for Final Cut Pro, Motion and Compressor states that the minimum requirements have changed from macOS Sierra 10.12.6 to macOS High Sierra 10.13.2 or later. In order to get today’s free updates for Final Cut Pro, Motion and Compressor, your Mac must be running 10.13.2 or newer. You won’t see these updates in the Mac App store if you are using an older version of the OS.