Please help - I'm not able to get a background image to load in the Outlook 2013 desktop app. It shows the bgcolor (which is good), but the image doesn't load. Any suggestions are greatly appreciated!

Here's the HTML for that section:

    <table class="hero" align="center" bgcolor="#626f7d" background="http://go.pardot.com/l/84982/2017-08-11/89mp8q/84982/110353/5Star_2017_Conversation.png" border="0" cellpadding="0" cellspacing="0" height="325" width="600" style="background-image:url(http://go.pardot.com/l/84982/2017-08-11/89mp8q/84982/110353/5Star_2017_Conversation.png); background-size: contain; display: block;" valign="top">
    <tbody>
        <tr>
            <td pardot-data="" scope="col" width="10" class="" >&nbsp;</td>
            <td height="325" pardot-data="" scope="col" style="color: #ffffff;" width="590" class="">
            <h1 style="line-height: 1.5; font-family: Arial, Helvetica, sans-serif; font-size: 30px; color: #ffffff;">LET'S<br>
            START A<br>
            <span style="background-color: #94bb1e; color: #ffffff; padding: 10px;">CONVERSATION</span></h1>
            </td>
        </tr>
    </tbody>
</table>

I've also added this CSS in the <style> tag:

<style type="text/css">
    .hero{
            background-color: #626f7d;

            background-image: url('http://go.pardot.com/l/84982/2017-08-11/89mp8q/84982/110353/5Star_2017_Conversation.png');

            background-repeat: repeat-y no-repeat;
        }