Child theme style is not working with cover news theme

Hi,
I have created a child theme for the ” CoverNews” theme using the plugin ” child theme generator”.
Whenever I apply a new style in the child theme ” style.css” no changes occur and the parent theme style still exists there.

for e.g To change the red background color of this ” .main-navigation” I placed new style in child theme style.css like this
.main-navigation {
background: #37a000;
}
and saved the file but not changes on the style and the parent style is still there. I have activated the child theme as well.

The page I need help with: [log in to see the link]