Hi Fredotty,
We see you're having some issues with getting alerts that there isn't a camera connected on your Mac. We can certainly understand the need to get that working, so that you can use the camera in applicable apps. We'd like to help out with that.
There's a helpful page setup here that should help out with that particular issue: If your built-in camera isn’t working on your Mac
Additionally, try disconnecting any accessories you may have connected to the Mac. If it's a desktop Mac, you can keep any mice/keyboards connected. If the issue still persists, try setting up a second Admin user on the Mac, switch over to that Admin user account, and see if it's still happening. This helps to note if it's a system-wide or user-specific issue. If needed, this page can help set up the new user: Set up users, guests, and groups on Mac
We hope that helps out.
Take care!