Like not kept after page refresh

Hello,

When a visitor (not logged user) like a post, the icon return to default state after refreshing the page.

For example:
1. A visitor like a post, the icon becomes as red heart.
2. The visitor refresh the page.
3. On the page, the icon go back to gray heart (instead of red).
4. When the visitor like the post again, the message “You unlike it” appears and the icon become as red heart… (instead of gray heart).

To sum up, the plugin doen’t retrieve the like/unline of a visitor.

Can you help?

Thanks.