Can’t Rotate

I understand that the Settings app on your iPhone 12 doesn't rotate. If other apps on your iPhone 12 rotate like they're expected to, such as the Camera app or Safari, not being able to change the orientation of the Settings app could be an expected behavior for your iPhone model. Changing display orientation is not available for all apps on specific iPhone models. For more information, please check out: Rotate the screen on your iPhone or iPod touch - Apple Support

If you're experiencing this behavior with all the apps on your iPhone 12, we'd recommend that you reach out to Apple Support directly. Here's how: Get Support

First try forced restart

Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the side button. When the Apple logo appears, release the button.