ECG function not working

I recently was given an Apple Watch Series 6 that was purchased about a year ago and never used.

My first attempt at setup of the Watch appeared to work, but in fact, my Apple ID had failed to register properly and the watch was only partially functional with a Bluetooth connection to the phone but limited access to my data. The Heart and ECG apps wouldn't work and failed to offer any useful error codes.

Verify your watch is "fully installed" and registered to your Apple ID... on iPhone: Watch > General > Apple ID [when not fully installed, the Watch app would just spin trying to "get" the associated Apple ID.

I reset/reinstalled and all the Health related stuff is working now.