/*
Theme Name: Flatsome Child
Description: This is a child theme for Flatsome Theme
Author: UX Themes
Template: flatsome
Version: 3.0
*/

/*************** ADD CUSTOM CSS HERE.   ***************/
add_filter('woocommerce_get_availability', 'availability_filter_func');
function availability_filter_func($availability)
{
$availability['availability'] = str_ireplace('Out of stock', 'Sold', $availability['availability']);return $availability;
}


I hope that helps to resolve your issue.
@media only screen and (max-width: 48em) {
/*************** ADD MOBILE ONLY CSS HERE  ***************/