smpl-skeleton callout shortcodes won't float

In a child theme of smpl-skeleton, I am using shortcodes as follows:

[one_half]
(image)
[/one_half]

[one_half]
[callout]callout text[/callout]
<h2>heading</h2>
paragraph text
[/one_half_last]

What I expect to happen is for the callout, heading and paragraph text to float up to the right of the image.

Instead the callout breaks as if it has been cleared and positions itself below the image.

Thanks in advance for any advice.

buddy