Today’s Final Cut Pro 10.4.1, Motion 5.4.1 and Compressor 4.4.1 updates require macOS High Sierra 10.13.2
Monday, 09 April 2018
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.
It is rare that Final Cut Pro needs such a relatively new version of macOS. Since 2011, the ProApps team have only required that the OS is as old as 16 months old.
This means that Final Cut will have access to parts of macOS introduced in last year’s Apple Worldwide Developer conference - the most likely feature being added will be eGPU compatibility - as introduced in the most recent update to High Sierra. Although parts of Final Cut Pro 10.4 and earlier can be sped up by attaching an eGPU, some core parts weren't.
If you haven't updated Final Cut Pro on your computer before, there is a support page from Apple that gives useful tips.