the camera or flash on my iPhone isn't working

Read and follow ALL the steps provided here:--> If the camera or flash on your iPhone, iPad, or iPod touch isn't working - Apple Support

If the issue persists, contact Apple Support using this link:--> Get Support

Regards

Giulio

Hi, it could either be due to a software update or hardware damage as the flash wont work without the rear camera. First thing to try is a restart. Check here https://support.apple.com/en-gb/HT201559 for info on how to restart your iPhone. If that does not work it may be hardware damage and you may need to have your rear camera replaced.