Hello manojadm,
Thank you for using Apple Support Communities. We see that Guided Access is greyed out in Accessibility Shortcuts on your iPhone. You've come to the right place! We're happy to help.
We recommend turning off Guided Access in Settings > Accessibility and then turn it back on. If the issue persists, restart your iPhone. Restarting can resolve many unexpected behaviors.
Let us know the results. Please include any other troubleshooting steps that you may have tried.
Have a nice day!