Just tried again - loads with no data and asks for a sign in. Different from the first though. First time took me to a different page for sign-in. This time it was a small pop-up block which then directs you to the different sign-in page. So yeah they are metering the viewers likely due to bandwidth and have been making it pretty as the day goes on.
The COVID-19 map is working fine this morning. That’s good.
https://gisanddata.maps.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6