AI not working in 16PRO in india

Review the Support Article here for additional support for languages/regions coming in April.

Apple Intelligence is available in English (Australia), English (Canada), English (Ireland), English (New Zealand), English (South Africa), English (UK), and English (US) in most regions around the world. In April, a software update will deliver expanded language support, with more coming throughout the year. Chinese, English (India), English (Singapore), French, German, Italian, Japanese, Korean, Portuguese, Spanish, Vietnamese, and other languages will be supported.

How to get Apple Intelligence - Apple Support

Also if the model number ends in CH/A, then the phone is intended for China distribution and is currently not able to support AI even by changing the region/language.

Apple intelligence is not available in India.

Apple intelligence information