Try to add the following PHP code snippet to the child theme functions.php file

function woodmart_get_products_per_page() {
		if( ! class_exists('WC_Session_Handler') ) return;
		$s = WC()->session; // WC()->session
		if ( is_null( $s ) ) return;
		
		if ( isset( $_REQUEST['per_page'] ) && ! empty( $_REQUEST['per_page'] ) ) :
			return intval( $_REQUEST['per_page'] );
		elseif ( $s->__isset( 'shop_per_page' ) ) :
			$val = $s->__get( 'shop_per_page' );
			if( ! empty( $val ) )
				return intval( $s->__get( 'shop_per_page' ) );
		endif;
		return intval( woodmart_get_opt('shop_per_page') );
	}