The camera on my Apple studio display does not work.

I have had it sometime and suspect it has never worked as I rarely zoom or FaceTime, but now realise when I do it is my Mac Book air camera that is working not my studio display. I am not very technical with these things . I have seen others have had a similar problem. I have tried going into privacy and security "camera" only google chrome (which I rarely use) and zoom (which I no longer have ) are shown as having access to the camera. How do I install FaceTime for example?