Panic. Google Chrome gave certificate errors on https:projecthours.net Turns out Chrome is not accepting certain ssl certificates any longer. See: https://knowledge.digicert.com/alerts/ALERT2562.html
So I updated the Project Hours web site to use a free Let's Encrypt certificate. Turns out it was quite easy to configure on Azure following this tutorial: https://www.tecklyfe.com/how-to-setup-lets-encrypt-ssl-certificates-for-an-azure-web-app/. And it there is an automated proces to renew the certificate every 90 days, which is great.