Site isn't re-adapting to mobile layout

Hello.

I’m using the Responsive theme and when I look at my site on my iPhone (or via a mobile phone emulator tool) the elements of the site aren’t stacking one on top of the other like they should.

The main menu properly shows itself as the mobile version. But everything else is all squished very narrow rather than stacking itself up one on top of another.

I’m using a child theme so I could make a slight change to post-meta.php but nothing drastic.

Any ideas?

Thanks!