Native Instruments Kontakt 4 was released in Feb' 2010 and Kontakt 5 was then released in Jan' 2012. Since the release of Kontakt 5 there has been many changes with computer operating systems; especially on Mac with OS X systems. The 10.12 Sierra update was released late 2016, with most major DAW software becoming compatible with the new update.
Users of the Native Instruments Kontakt 5 engine have had no compatibility issues when loading in the newest OS X 10.12 Sierra. As long as the newest Kontakt update (5.6.8) has been installed. To see if your system is supported, see the Kontakt system requirements page here.
If you are experiencing any problems with the Kontakt 5 player, please ensure you are running the newest update as this should resolve any issue you are having, again please see the article here to check the system requirements you will need to run Kontakt 5. To check you are update to date, or any updates are available to you, please use the Native Access application under the 'Available Updates' tab.