Admin cannot insert Google Maps embed code in widget

I want to insert the following GMaps iframe (comes directly from GMaps by doing a search, and then Sharing > Embed > Small) into a text widget in a sidebar. This works when I do it as a Super-Admin, but doesn't work when I do it as a subsite Admin. The code simply disappears after I click Save on the widget. Weird!
<iframe src="https://www.google.com/maps/embed?pb=!1m18!1m12!1m3!1d3072.816026778646!2d-84.1437626844224!3d39.631346010951376!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x88408faa4551db63%3A0xcd7a16eab19be296!2sAvenues+To+Wellness+Yoga!5e0!3m2!1sen!2sus!4v1472218460622" width="400" height="300" frameborder="0" style="border:0" allowfullscreen></iframe>

I don't want to add a maps plugin, and it works so well as a SuperAdmin -- why can't my subsite Admins do this?

Thanks for your help!