Hi there,
Thank you for the login information. I think I found the problem. While I was checking the front end of the website I see this error on my Google Chrome Browser console:

The error basically says that the browser blocks the content of the Calculator because it is served as HTTP and not HTTPS. And because your website is the server with HTTPS then it is considered as an insecure content and browser blocks the calculator.
I suggest that you change the iFrame address and add it with and s so it will be https://...... I am not sure if that will work as the content itself also should be served through SSL. So you need to contact the Calculator developer and ask them to make it work with HTTPS.
Thank you.