iframe embed not working in wordpress?

Hi there

I am trying to embed an iframe with another website in the center of a page on my site ( site is https://www.mcmsalem.com/map)
instead what shows up is https://www.mcmsalem.com/map/?preview_id=2054&preview_nonce=dda64f58ef&preview=true- with a bad gateway error.

instead it is just throwing lots of disconnection and weirdness around. I have tried lots of different iframe codes and I have an iframe embed plug in also.

Any suggestions?

Thank you so much!