The same is happening to me – I’m doing it on a local dev environment so I can’t show it to you on a live site, but here is the resulting markup:
<span itemscope itemtype="https://schema.org/Article" class="itempropwp-wrap"><!-- ItemProp WP 3.4.1 by Rolands Umbrovskis https://umbrovskis.com/ --><meta itemprop="name" content="Sample Post With Image Aligned Left"><meta itemprop="url" content="https://local.test/image-aligned-left/"><meta itemprop="author" content="https://local.test/author/testuser/"><meta itemprop="description" content="This is an example of a WordPress post, you could edit this to put information about yourself or your site so readers know where you are coming from. You can "><meta itemprop="datePublished" content="2013-09-01 01:57:05"><meta itemprop="interactionCount" content="UserComments:1"/><!-- ItemProp WP 3.4.1 by Rolands Umbrovskis https://umbrovskis.com/ end --></span><span itemscope itemtype="https://schema.org/Article" class="itempropwp-wrap"><!-- ItemProp WP 3.4.1 by Rolands Umbrovskis https://umbrovskis.com/ --><meta itemprop="name" content="Sample Post With Image Aligned Left"><meta itemprop="url" content="https://local.test/image-aligned-left/"><meta itemprop="author" content="https://local.test/author/testuser/"><meta itemprop="description" content="This is an example of a WordPress post, you could edit this to put information about yourself or your site so readers know where you are coming from. You can "><meta itemprop="datePublished" content="2013-09-01 01:57:05"><meta itemprop="interactionCount" content="UserComments:1"/><!-- ItemProp WP 3.4.1 by Rolands Umbrovskis https://umbrovskis.com/ end --></span>
-Wordpress: 3.9.2
-Genesis 2.1.2
-Trestle Child Theme (Basically same as Genesis Starter Theme
-Yoast SEO Plugin Installed
-itemprop-wp 3.4.1
Thanks for any help you can provide – I really appreciate your plugin.