When attempting to navigate to a URL that opens within the iFrame, usually coming from a subform, results in the following error in the Console (F12):
"Refused to display '[URL]' in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'."
This is a limitation created from the domain of the site we are trying to hit. The site's owner has set the header to SAMEORIGIN, which means that they have disallowed loading of the resource in an iFrame outside of their domain.
The functionality works without issue if the page is loaded in a new window, rather than through an iFrame.
For more information on the X-Frame options, please see the following article: