Please open System Preferences on your Mac and go into the Security & Privacy pane.
The Privacy tab will have options to block or allow applications to access your Camera and Microphone. Please ensure that the HUE software you want to use has permission to access both the camera and the microphone; this should unlock the video and audio features in the software.
If the software is missing from the list, removing it and then reinstalling it to the Applications folder should cause macOS to detect it properly. Please contact us if you are having any additional trouble with the Mojave operating system update.