This plugin hasn’t been updated in almost two years, so you should consider finding a new one.
That said, in this cases you have to open1 the plugin files and search for some string related to your issue, e.g., post_type.
You’ll find that in the file functions.inc.php, it has two occurrences of:
AND a.post_type="post"
Change that to:
AND ( a.post_type="post" OR a.post_type="YOUR_CPT_SLUG" )
Not sure if that’s the only thing that needs to be changed, but now you should be able to further inspect it and locate other parts that need modification.