Devilirium

It is arcade game site, so it is heavily customized.

sorry im not a coder, just a normal user of wordpress, so my suggestion based on what i investigate:

1. To understand in what section the error appears (by google tool). Look .php page where it appears. Try to play with code, and look for closing things like <div>. For me it was like hundred times of fail and trial =)

2. Contact developer. I bet it is something in his code, so if you paid for theme, you have all rights to get the answer from professionals

Just solved this problem for myself. Dont know if it help you a lot, because it is specific.
My case:
Plugin was ok – thank you for it, Lester.
The issue was in my theme. I found, that Google shows error in Item Type schema.org/SoftwareApplication.
Then i found it in my theme code. And noticed that https://schema.org/AggregateRating was inside <div> of https://schema.org/SoftwareApplication.
I just moved </div> right before rating

Below the code

<div itemscope itemtype="https://schema.org/SoftwareApplication">
      <meta itemprop="name" content="<?php the_title(); ?>" />
      <meta itemprop="image" content="<?php myabp_print_thumbnail_url(); ?>" />
      <meta itemprop="description" content="<?php echo get_the_excerpt(); ?>" />
      <meta itemprop="softwareApplicationCategory" content="GameApplication" />
	  </div>
      <div itemprop="aggregateRating" itemscope itemtype="https://schema.org/AggregateRating">
        <span itemprop="ratingCount"><?php echo $ratings_user; ?></span> <?php _e('votes','xl'); ?>, <?php _e('average:','xl'); ?> <span itemprop="ratingValue"><?php echo $rating_average; ?></span>/<span itemprop="bestRating"><?php echo $ratings_max; ?></span>

    </div>