Why doesn't the screen on my iPad rotate?

Pull the control center up from the bottom of the page and see if you turned anti-rotate on by accident.

Do you see a lock icon in the upper right corner of the screen - if you do then the screen orientation is locked.

Try the side switch above the volume rocker first and see if that unlocks the screen. If that didn't work, then swipe up from the bottom to get to the control center and look for the lock icon in the top row on the right.

If the screen is unlocked but still will not rotate, reset the iPad.

Reset the iPad by holding down on the sleep and home buttons at the same time for about 10-15 seconds until the Apple Logo appears - ignore the red slider - let go of the button