The star class lacks background-position

.star{
// ...省略
background-position: 0 -13px;
}

Update
The last span class should be written like this

<span class="star no-star"></span>

It is not displayed yet. Check the image path. Can you access it by writing it directly?
Or check again whether the style is overridden.

According to your code, you want to write three yellow stars and one gray star. If this is the case, then your last class should be .star .no-start

Added .star .no-star, it will not be displayed either