FaceTime camera not receiving video

I spent hours debugging this on my MacBook Pro (Retina, 13-inch, Early 2015) running Catalina. The camera did not work in any app.

I tried restarting, zapping PRAM, resetting SMC. In System Preferences, I checked permissions in Security & Privacy > Privacy > Camera.

In About This Mac > System Report…, the camera shows up correctly in Hardware: Camera.

I discovered that the camera did work in another user account, so it was not a hardware problem.

Long story short, I figured out that Screen Time > Content & Privacy Restrictions were inadvertently turned on, with Apps > Allow: Camera being disabled. I had turned on restrictions on an old iPhone; these settings are apparently shared across devices for the same iCloud account.

Test it using a new account (create one) or (after making a backup) on a fresh install. If that doesn’t work, the camera is defective. The USB interface and power indicator can still work with a broken video module, so the green light does not always indicate a working camera.

The camera has failed.

It's not an expensive part, but you have to disassemble the entire LCD display assembly to remove it. Since the assembly is glued together, it makes replacing this part extremely difficult.

Therefore, you have two options:

• replace the entire display assembly
• get a USB web cam

(IMO) given the age of this laptop and the expense and difficultly of the repair, I would go with the second option.