Hello,
We just added a fix regarding that issue, the solution will be to edit the "administrator\components\com_hikashop\classes\discount.php" file and change that line :
$query = 'SELECT COUNT(order_id) AS already_used FROM '.hikashop_table('order').' WHERE order_user_id='.(int)$user_id.' AND order_status NOT IN ('.$cancelled_order_status.') AND order_discount_code='.$db->Quote($coupon->discount_code).' GROUP BY order_id';
By :
$query = 'SELECT COUNT(order_id) AS already_used FROM '.hikashop_table('order').' WHERE order_user_id='.(int)$user_id.' AND order_status NOT IN ('.$cancelled_order_status.') AND order_discount_code='.$db->Quote($coupon->discount_code);
Thank you for your feedback !