You have to allow Philips Hue Sync as a system software for your Mac. Go to System Preferences Security & Privacy > General, and allow the system software by Philips Lighting B.V. You must restart Hue Sync afterwards.
If you did not do this during the installation of Hue Sync, the Allow button may not be visible anymore. You can make it reappear by hovering over the Music mode button in Hue Sync, and press the Retry button on an account with administrator privileges.
If clicking the Allow button doesn’t work, then please try to close all other programs which may be interfering with the mouse input, and make sure you access your Mac locally.