Let's Encrypt: ClientID reqistered under application settings differs from what I entered?
The checkbox "Update Application Settings" must be checked if you want to modify the settings from the Let's Encrypt extension's pages.
If you hate the idea of an azure webjob swallowing valuable system resources of your azure app service then there is now an alternative solution which uses Azure Automation;
https://www.powershellgallery.com/packages/GetSSL-LetsEncrypt
Documentation @ https://w.itpro.es/ssl-eng