Back camera and Flash not working

I split this question off from your original ask. I'm not sure if you also have an iPhone 8, but this is a similar answer in most cases for iPhones. Perhaps you can provide some more clarity if that's needed.

The enable signal for the flashlight comes through the camera module. So if your camera isn't working correctly, neither does the flash. More than likely, you need a new rear camera to resolve this. But any additional details about the device's history, if anything happened prior to the failure, could help narrow down the cause.