CSS Animation of pseudo-elements is not working in FF

Question

I tested this css loop in Chrome and Safari - works good. But the animation is not working in Firefox and IE.

Where is the problem? I defined the -moz- prefix already. Or should I stop using css transitions for pseudo-elements?

/* fullscreen div */
section_2.cd-single-project.is-loaded.is-full-width:after {
top: 0;
left: 0;
height: 100%;
width: 100%;

/* name */
-webkit-animation-name: fading; 
-moz-animation-name: fading;
-ms-animation-name: fading;
-o-animation-name: fading;
animation-name: fading;

/* count */
-webkit-animation-iteration-count: infinite;
-moz-animation-iteration-count: infinite;
-ms-animation-iteration-count: infinite;
-o-animation-iteration-count: infinite;
animation-iteration-count: infinite;

/* duration */
-webkit-animation-duration: 12s;
-moz-animation-duration: 12s;
-ms-animation-duration: 12s;
-o-animation-duration: 12s;
animation-duration: 12s;   
}

/* fade safari */
@-webkit-keyframes fading {
0%   { background-image:url("1.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
25% { background-image:url("2.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
50%   { background-image:url("3.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
}

/* fade firefox */
@-moz-keyframes fading {
0%   { background-image:url("1.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
25% { background-image:url("2.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
50%   { background-image:url("3.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
}

/* fade opera */
@-o-keyframes fading {
0%   { background-image:url("1.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
25% { background-image:url("2.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
50%   { background-image:url("3.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
}

/* fade general */
@keyframes fading {
0%   { background-image:url("1.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
25% { background-image:url("2.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
50%   { background-image:url("3.jpg"); background-repeat: no-repeat;background-position: center center;background-size: cover; }
}

Answer 1

Can you try to add "animation-fill-mode: both" to see something. What is hapenning, I think, is that maybe the animation is already over or isn't triggered.

Answer 2

section_2 is not a valid selector unless custom element <section_2></section_2> is within html ?

Is section_2 a class of an element , missing . .section_2 ?, or an id of an element missing # #section_2 ?