Lorraine99 Said:
"There is no connected camera on my MacBook Pro: All of a sudden the built in camera cannot be detected. It is a MacBook Pro (13-inch, 2016, Two Thunderbolt 3 ports). I've tried a couple of on line solutions but was unsuccessful."
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Reinstall the macOS:
The drivers went missing somehow. So, reinstall the macOS. Nothing would be deleted. It's just that items that have become corrupted or deleted, would be replaced or reinstalled back to where they should be. Go Here: How to reinstall macOS from macOS Recovery - Apple Support.
Important: Be certain to create a backup of your Mac prior to all of this. That way, you can have something to restore from the Mac from, should anything go wrong with the reinstall.