Why is camera on my iPhone 13 Pro Max not working?

Follow the article below for step-by-step guidance.

⇢ If the camera or flash on your iPhone, iPad, or iPod touch isn't working - Apple Support

If the camera on your iPhone is still not working, make a reservation at your nearest Apple Store or Apple Authorized Service Provider to get in-person support. ⚛️

⇢ Genius Bar Reservation and Apple Support Options - Apple

⇢ Find Locations

No one can tell you why. This is a user to user only forum.

See this link and try the solutions recommended, but if none help, then you'll need to schedule an appointment at your Apple Store Genius Bar for evaluation and options --> If the camera or flash on your iPhone, iPad, or iPod touch isn't working - Apple Support