It does work after accepting the security risk mentioned below. I think you need a valid SSL certificate for the iFrames to work.
Have you tried fixing the certificate for this URL? I think you can use cloudflare to get free SSL.
Edit: I guess this is not your site, but some third party you used, anyhow, I think that is the issue with this site.
This server could not prove that it is **chat.pitchly.net** ; its security certificate expired 162 days ago. This may be caused by a misconfiguration or an attacker intercepting your connection. Your computer's clock is currently set to Friday, June 28, 2019. Does that look right? If not, you should correct your system's clock and then refresh this page.
[Proceed to chat.pitchly.net (unsafe)](chrome-error://chromewebdata/#)