Many thanks to those fellow community members who stopped by to offer help and advice.
From what I've discovered it appears the Esri website architecture operates tracking cookies, since my browser has been configured to protect my privacy it consequently does not display correctly the World Map Way-back Imagery app.
That the app works fine in the notoriously insecure and data-sharing Microsoft Edge looks to support that as the cause.
Just how much data is being tracked and harvested will be a concern to anyone who values their online privacy.