Some customers could have their screen rotation locked, due to their device settings. If they turn their device to landscape view and customer's picture does not change/rotate, be sure you ask them to unlock their rotation. They can change it through the Settings option on their device.
On iPhones, instruct the customer to swipe with their finger upwards from the bottom of the screen to access the quick menu and see the lock screen icon in the top right corner. Tap on it to unlock the screen.