- Check your system settings: 
Go to ‘Settings > Display & Brightness > ‘ and make sure ‘Auto-Rotate’ is turned ‘On’.
 - Check your app settings: 
Go to the app you are viewing and check to make sure ‘Auto-Rotate’ is turned ‘On’.
 - Check your device’s physical button: 
Your device may have a physical rotation lock button. Check and make sure this button is not currently active.
 
