Hi there Prashant2429,
Thanks for reaching out to Apple Support Communities. We see you're experiencing some difficulties with enabling Face ID and see you came to us from a helpful support article for this issue. Were you able to follow the steps listed there and update your device to the latest iOS? If not, we'd recommend first starting there and see if that resolves this for you. If you continue to get the same message, you'll need to reach out to Apple Support for further assistance. You can see your available support options using the link below.
Take care.