Include related to this post function

Hello,
Thank you for this great plugin.
When I use the “include related to this post” function, there are many posts I can’t find using the search bar.
I don’t know what is going wrong because all category are included in the setting page and none excluded, so I should find all the posts, right ?
Anyway, is there another way to find and include the posts I can’t get using the search bar ?
Best regards,
Tamenori

https://www.ads-software.com/plugins/yuzo-related-post/