iPhoneX screen won't rotate from portrait to landscape mode

I have tapped the unlock button from lock to unlock but it still will not rotate

Reboot your iPhone and see if that helps:

Press and quickly release volume up button

Then press and quickly release volume down button

Then press and hold the power button (keep holding past swipe to power off) until the Apple Logo appears, then let go

From the upper right hand corner of your iPhone screen swipe down to open control Center. Tap the icon with a lock in it to permit rotation.