When trying to disable Automatic Certificate Management (ACM) with
heroku certs:auto:disable I see the error
certs:auto:disable is not a heroku command.
This error message is shown when using outdated versions of the Heroku Command Line tools. Download and install the latest version to fix this using the instruction here https://devcenter.heroku.com/articles/heroku-cli
For users who are still having trouble, please check to see if you have the legacy
heroku gem installed and follow the steps here https://devcenter.heroku.com/articles/heroku-cli#uninstalling-the-legacy-heroku-gem to remove it.