If your iPhone display does not go into landscape mode or does not rotate, follow the steps below:
Verify that the Screen Rotation Lock is Off
STEP 1: Double-click the Home button to display the recently used apps.
STEP 2: Flick from left to right along the bottom of the screen until you see the Screen Rotation Lock button.
NOTE: The Screen Rotation Lock button will appear to have a padlock when it is turned on.
STEP 3: Tap the Screen Rotation Lock button located on the bottom left corner of the screen. The padlock in the Screen Rotation Lock should now disappear.
STEP 4: Test if the display will now go into landscape mode or will now rotate. Otherwise, proceed to the next instructions.
Test the Screen Rotation
Not all iOS apps are designed to rotate. Certain apps and features may support only one mode, either landscape or portrait. For example, Video apps plays videos in landscape mode whereas Reminders use only portrait mode.
STEP 1: On the Home screen, tap Utilities, then tap Calculator while holding the iPhone vertically (portrait mode). The standard calculator should appear.
STEP 2: Rotate the iPhone to a horizontal position (landscape mode). This should display the scientific calculator.
If the screen does not rotate as expected while using the Calculator app, proceed to the next instructions.
Restart the iPhone
STEP 1: Press and hold the Sleep/Wake button for a few seconds until the red slide to power off slider appears, then slide the slider from left to right.
STEP 2: Press and hold the Sleep/Wake button until the Apple logo appears.
STEP 3: Test if the display will now go into landscape mode or will now rotate. Otherwise, proceed to the next instruction.
Back Up and Restore Your iPhone
If the same problem persists, back up and restore your iPhone. For further instructions, click here.