2 colomn set-up

Hi,

I’m creating a contact form and I need it to be displayed in 2 colomns.
Last year or so I created one with the code below, but somehow now it’s displayed vertical and not next to each other.

Can anyone tell me why it doesn’t work anymore?
Thanks in advance!

BTW; A placeholder is active, so I can’t show you the form itself.

<div id=”responsive-form” class=”clearfix”>

<div class=”form-row”>
<div class=”column-half”>Naam * [text* your-name]</div>
<div class=”column-half”>Bedrijfsnaam [text company-name]</div>
</div>

<div class=”form-row”>
<div class=”column-half”>Email * [email* your-email]</div>
<div class=”column-half”>Onderwerp * [text* your-subject]</div>
</div>

<div class=”form-row”>
<div class=”column-full”>Bericht * [textarea* your-message]</div>
<div class=”column-full”>[response]</div>
</div>

<div class=”form-row”>
<div class=”column-full”>[submit “Verzenden”]</div>
</div>

</div>

The page I need help with: [log in to see the link]