Online Store editor session can't be published

[Boo_Cottage]

Hello,

I'm trying to make a google map responsive so it changes dimensions on different devices. I thought I'd figured it out in the CSS section with the following (and it looks like it's working on my screen with the different device views):

.google-map {
padding-bottom: 50%;
position: relative;
}
.google-map iframe {
height: 100%;
width: 100%;
left: 0;
top: 0;
position: absolute;
}

But now I can't save my page - I get the message "Online Store editor session can't be published" have I done something wrong?! Completely new to shopify so struggling to get my head around where things go to be honest!

I've put the google map link into the page section using the following html: <div class="google-map">
<div data-name="subheading-text" class="editable-element editable-element--text text subheading"></div>
<iframe src="MY MAP LINK" style="border: 0;" allowfullscreen="" loading="lazy" referrerpolicy="no-referrer-when-downgrade" width="600" height="450"></iframe></div>

I've tried it on different devices and different web browsers and it's saying the same thing. Using Dawn theme if that helps.

Hope someone can help!

Thanks, Nic