Phone Screen Won't Rotate!

What are the reasons a phone screen won't rotate when it should? The first course of action should always be to check the Quick Settings menu. Swipe down from the top of the home screen, and check that the auto-rotate feature is enabled. If it is, it will be blue, and if not, it will be greyed out and display a lock. Sometimes this feature is removed from the Quick Settings accidentally, or the settings are rearranged and it is not immediately visible. In this case, check all pages of the Quick Settings and if it's not there, enter More Options in the upper right, then Edit buttons, then tap and hold the feature, and drag it back to the Quick Settings menu wherever you'd like. Tap Done to lock the setting. If the function is enabled but the screen will not rotate, try a device restart. If that's not working, try booting the phone into Safe Mode. If none of these work, schedule service.