If the Seller does not ship your item within “Seller sells in” + 1 day, then you will be presented with the option to cancel the order in the details screen. If the seller creates a Shipping Label, then the counter restarts and you will have to wait an extra 1 day from this action. These are the only cases where the Buyer can cancel an order.
Please note that if the Seller has marked the listing as Shipped, then the option to cancel the listing will not appear.
If you believe that the Seller still hasn't shipped the item out after marking it as Shipped. Please contact Support and we can look into the transaction and assist with the cancellation.
When an order is cancelled, the Seller gets an automatic "Poor" rating. The Buyer is not rated in a cancellation.