FaceTime HD Camera (built in) isn't working

Have you looked at this Apple Support article? If FaceTime isn't working on your Mac - Apple Support

If it doesn't work in the Photo Booth app, that rules out FaceTime as the issue. You'd then want to look at this Apple Support article: If the built-in camera isn’t working on your Mac - Apple Support

Hope this helps.

I'd recommend making an appointment at your Apple Store's Genius Bar and let them take a look at this issue: Genius Bar Reservation and Apple Support Options - Apple

Macs don't have user-accessible drivers for built-in hardware as some Windows computers do, so that's not an option.

The only other thought that comes to mind would be to ask if you have any anti-virus, app "cleaners", Mac "optimizers" or VPN software installed? These almost always create more problems than they prevent, and I always recommend using the software publisher's uninstaller to erase them from your Mac.

Regarding Norton anti-virus, you'd be hard pressed to find anyone volunteering on these Discussion pages that endorses the use of any anti-virus program. They're simply not needed on a Mac, as a Mac requires user permission to install anything. Furthermore, these programs actually create more issues than they prevent. My experience tells me the question isn't IF an anti-virus can create issues, it's only a matter of WHEN.

I'm not saying Norton is definitely the root cause of your camera issue, but it could be. The choice is yours, of course.

When you uninstalled it, did you use Norton's uninstaller, or did you simply drag the application to the Trash?

If you didn't use their uninstaller, the application isn't truly uninstalled, as there are a lot of support files and extensions left behind that can cause issues if not deleted. I recommend you reinstall Norton, then go to the Norton folder in Applications and see if there's an uninstaller there. If not, you'll want to Google "How to Uninstall Norton Anti-Virus on Mac" to learn how to properly delete it.