ECG app not available on Apple Watch series 4

Thanks for asking about the new ECG feature. 

Check here for availability in your region: ECG

ECG requires the following software: 

• The iPhone must have iOS 12.1.1 or later installed
• The Apple Watch must have watchOS 5.1.2 or later installed

For additional help with the ECG feature on your Apple Watch, take a look at these articles.

Heart rate notifications on your Apple Watch - Apple Support

Taking an ECG with the ECG app on Apple Watch Series 4 or later - Apple Support

If you have any other questions please reach out to our team here: https://apple.co/HeartFeatures. If you believe that you are experiencing a medical emergency, please dial your local emergency services.

Take care

Where was your Watch purchased?

I am facing same problem. I am staying in india and updated phone and watch to latest version. During my dubai visit, I have purchased watch from dubai.

That is why it is not working, you purchased it in Dubai where it is not approved yet.