Back camera not working at all and not able to record video.

I’ve got an iPhone XR, and it is in great condition, cameras seem to be intact from the outside and no damage to any part of the phone, yet for some reason the back camera does not work with any camera application, and in the iOS camera app, the button to take a picture pops when held down or pressed and does not work? I’ve tried everything online, contacted support, yet nothing helped. For my video issue, using the back camera of course is not even an option, however when using the front camera the recording starts, and half a second later goes black and stops the recording. In the camera roll, the video is completely black, and when trying to play it, I get an error saying it cannot load the video. Once again, I have tried everything to fix it, Apple support still couldn’t help with it.