Not working ECG

Please see the notes in Taking an ECG with the ECG app on Apple Watch Series 4 - Apple Support and particularly the list of countries where ECG is currently released.

It depends not he region your Watch was purchased from, the region your Apple ID is set to, and the region you are currently in. All three conditions must be a yes for the ECG app to work on your Watch.

Apple can’t make the ECG app available in any country until the government regulator grants permission. Like it or not, that is the law in almost every country where Apple does business and Apple’s management have no wish to risk their careers by getting themselves or the company prosecuted.