ECG Feature not working

Which country are you in though? You actually need to be physically located in the US for it to work.

 

There’s your answer then I’m afraid.

 

Check your PM
Make sure the watch region is also set to the US, install a VPN app in your phone and see https://goo.gl/JR9Mey.
Take a look at the video below

 

This does not work unfortunately. The only ones that seem to work are those whose model numbers end in LLA.