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>
