A few days after creating a cert for my domain I received an email from Google:
Google has detected that the current SSL/TLS certificate used on https://www.example.com/ does not include https://www.example.com/ domain name. This means that your website is not perceived as secure by some browsers.
I created my cert using instructions from PythonAnywhere Help.
I also tested my site in many browsers - there are no warnings of any kind.
SSLLabs grade of my website: A