Q: Auto rotation stopped

Not all screens will rotate from portrait to landscape. Are you sure this is a screen that will rotate? If you are, makes sure the orientation lock is not on. Go to the Control Center and the lock is the last icon in the top row. If it is white, it is on, black and it is off. You may want to turn if on and back off it was off. You can also do a reset on the phone. This will not affect any data. Hold the sleep/wake and home buttons together until you see the Apple logo and then release. The phone will reboot. Test.

To expand on what ChrisJ4203 said:

If the screen doesn't rotate on your iPhone, iPad, or iPod touch - Apple Support

Take a look at the link from javaliga. If that does not help, then contact Apple Support.

govilpune wrote:

 

still nothing...

You contacted Apple Support and nothing happened?

If the orientation lock has failed, then that means there is a problem with the gyro in the phone, and that is a hardware error and would require replacement of the device. This can affect your compass and other things that rely on the gyro. How you decide to proceed after completing all of the troubleshooting steps is up to you. Good luck.