ECG App not showing on Model A1977, US locality, watchOS 5.3, iPhone X iOS 12.4

A few days ago I bought a Series 4 Space Gray Aluminum watch, paired it with my iPhone X and attempted to run an ECG reading. The app did not show on the watch, so I looked up how to do it and no luck, so far. I've read https://lifehacker.com/if-you-cant-set-up-your-apple-watchs-new-ecg-app-heres-1830936317, and a few other forums, including here. The watch and my account are US, so I'm not sure why it would not work. I've gone to the `Health` app, `Health Data` -> `Electrocardiogram (ECG)` menu, and nothing comes up to set it up. I followed the instructions in the link above and there is no option for `Set Up the ECG App in Health`. I've run out of things to try and check, hopefully someone here maybe has something to try. Oh, and yes, I've unpaired and re-paired it twice, as a new watch (no backup restore), and I've powered it on/off a few times.

Thanks in advance for any help.

Edmund