if order.sent?

    else

  order.cancel

  respond_to do |format|

    format.html { redirect_to request.referer.include? "cancel" ? request.referer : order_path(order.shopify_id), notice: 'Order cancelled successfully!' }

    end
  end
end

<div class="card-body">

      <%= link_to 'Cancel', order_path(@order.shopify_id), method: :delete, class: 'btn btn-danger' %>
    </div>