Apple Watch ECG does not work in India

India is listed as supporting ECG in the Apple Watch features list

https://www.apple.com/watchos/feature-availability

Did you buy the Series 9 in India, or did you purchase it in a country that does not support ECG? Check the above feature availability list for the country where you purchased your Apple Watch.

If you purchased it in India, from an Apple authorized retailer, or directly from Apple, then it is most likely an Apple Watch made for India.

If you obtain it 2nd hand, it might be from somewhere else. HOWEVER, the Series 9 is rather new to be sold second hand.

I would contact

Contact – Official Apple Support (IN)

I think this is the India Apple Support URL.

Have your Apple Watch serial number handy

Apple Watch-> Settings-> General-> About-> Serial Number

They should be able to tell you if your Apple Watch was intended for the India market.

If it was, then you can ask about ECG at the same time.