Elementor ElementPack iframe – Auto Height for cross domain

Hello, I am using the plugin ElementPack and using the Iframe widget to embed a website from the root domain (app.boostboxpr.com) and my other domain (partners.boostboxpr.com). The auto height options in the widget works just fine for app.boostboxpr.com, however when putting a website from partners.boostboxpr.com the auto height doesn’t work.

The widget states that “Auto height only works when cross domain with ‘allow origin all in header’.”

From brief research it sounds like since partners.boostboxpr.com is a cross domain, then I need to do some additional steps to make this work. However I need assistance in knowing how to do this.