Hi Trong,

This is a small CSS conflict with your current active theme or other plugins. Please leave your forum URL to allow us to check it. 

Here's please: http://expressbustosapa.com/community/

Hi @trong,

This is a conflict with your theme. Please put this CSS code in Dashboard > Forums > Settings > Styles Tab > Custom CSS Code textarea. Save it, delete all caches, navigate to forum front and press Ctrl+F5:

#content article #wpforo #wpforo-wrap ul li {
    clear: inherit; float: inherit; width: inherit; background-image: inherit; background-position: inherit; background-repeat: inherit;
}

Thank you so much! It works well now!