Impossible to have an image on the haeder

Hi everybody !

It has been now 3 days since I look for the solution to my problem and I hope that you can help me. What I want is simple: i want that appears an image on the header.

When I tested my website in my computer with Wamp (local server), I had coded this (in expound.css) and my image appeared and it worked:

`.site-header .site-branding {
position: relative;
min-height: 154px;
background-image: url(images/logo-mfc.png) no-repeat;
}
.site-title-group {
position: relative;
margin: 50px 40px 50px 180px;
}

Now my website is online. But when I rewrite this code, nothing happens. The image does not load (failed to load the given url). However, my image is in the good file in my ftp: /www/wp-content/themes/expound/images/logo-mfc.png

I think I exhausted all the solutions which I could try. And which I don’t understand is that when i put a bakcground blue for example, it works: .site-header .site-branding {background: blue;}

So, somebody would have a solution ? I know that the subject was already approached on some previous subjects but I tried to apply the brought answers and it do not work either. Thanks for all