ECG not working in my Apple Watch 10
Set-up option not appearing when opening ecg app in Health app
Apple Watch Series 10, watchOS 11
Go through this app and make sure you've configured everything you need to --> Take an ECG with the ECG app on Apple Watch - Apple Support
Also, since this is about Apple Watch and you have posted to the iPhone forum, I have asked moderation to move this post to the Apple Watch forum. Check there if you don't see it here shortly.
Finally, out of curiosity, where was this watch purchased? My understanding is that if, for example, the watch was purchased in China, ECG, likely won't work on the watch, regardless of where you are.
