Firefox has a bug which causes the top and bottom padding to not work if the padding is using percentage values.
Add this into the Custom CSS box located in your Salient Options panel (Make Sure there are no red cross in the Box) :
/*Firefox Padding Issue, workaround is to use viewport width parameter*/
.wpb_row .span_12 > .col.padding-1-percent, .column-inner.padding-1-percent { padding: 1vw; }
.wpb_row .span_12 > .col.padding-2-percent, .column-inner.padding-2-percent { padding: 2vw; }
.wpb_row .span_12 > .col.padding-3-percent, .column-inner.padding-3-percent { padding: 3vw; }
.wpb_row .span_12 > .col.padding-4-percent, .column-inner.padding-4-percent { padding: 4vw; }
.wpb_row .span_12 > .col.padding-5-percent, .column-inner.padding-5-percent { padding: 5vw; }
.wpb_row .span_12 > .col.padding-6-percent, .column-inner.padding-6-percent { padding: 6vw; }
.wpb_row .span_12 > .col.padding-7-percent, .column-inner.padding-7-percent { padding: 7vw; }
.wpb_row .span_12 > .col.padding-8-percent, .column-inner.padding-8-percent { padding: 8vw; }
.wpb_row .span_12 > .col.padding-9-percent, .column-inner.padding-9-percent { padding: 9vw; }
.wpb_row .span_12 > .col.padding-10-percent, .column-inner.padding-10-percent { padding: 10vw; }
.wpb_row .span_12 > .col.padding-11-percent, .column-inner.padding-11-percent { padding: 11vw; }
.wpb_row .span_12 > .col.padding-12-percent, .column-inner.padding-12-percent { padding: 12vw; }
.wpb_row .span_12 > .col.padding-13-percent, .column-inner.padding-13-percent { padding: 13vw; }
.wpb_row .span_12 > .col.padding-14-percent, .column-inner.padding-14-percent { padding: 14vw; }
.wpb_row .span_12 > .col.padding-15-percent, .column-inner.padding-15-percent { padding: 15vw; }