The salient theme wraps embedded videos (such as YouTube) in an element which causes an issue with sizing in our plugin. To fix this, add the following JavaScript to your site. This can be done manually using a custom JavaScript plugin. For further information see our documentation here.
setTimeout(function(){
$('#cff .cff-item iframe').each(function(){
if( $(this).parent().hasClass('iframe-embed') ){
$(this).unwrap();
}
});
}, 3000);
And add this CSS to your preferred custom CSS location or stylesheet. One option is the default additional CSS location found at WordPress Dashboard > Appearance > Customize > Additional CSS.
#cff iframe[src]{ opacity: 1; }