Thank you for contacting us and I'd be happy to assist.
Can you please share temporary admin login details along with the link to a page where this iframe's code can be seen? I'll be in a better position to guide you accordingly.
Note: Your next reply will be private and though no changes will be made on your website, please make a complete backup copy, before sharing the access details.
The way Elementor's shortcode widget processes the before and after content, it converts the HTML code for the iframe into special characters or HTML entities.
Also using a text widget to mix the field's shortcode and HTML also doesn't work, since the builder seems to strip the iframe code.