Most Viewed posts won't show

Hi,
The Latest Posts function works great on my site. However, when I turned it into “show the Most Viewed posts”, then it won’t show any posts.
http://haowoo.tw/blog
You can see on the right sidebar, the Last Posts is working fine; and the Most Viewed Posts isn’t showing anything.

Thank you for the great plugin!

https://wordpress.org/plugins/yuzo-related-post/