Why is my iPhone 7 Plus back camera not working and the flash/flashlight
not sure why it’s doing this, I updated to iOS 12 at least three weeks ago and camera/flash have been working fine until today
Read this support guide:
If the camera on your iPhone, iPad, or iPod touch isn't working - Apple Support
If you get no help, make an appointment at your most convenient Apple Store or Authorized Service Provider, and have your iP7+ inspected:
Apple - Find Locations - Location Selector
Regards
Giulio