It depends on what option you chose when the transaction was cancelled, if you choose Buyer made mistake or changed mind, it should not count as a defect.  Is that the reason you chose when requesting the cancellation?  Did the buyer agree to the cancellation?  If they didn't agree, or ignored the request, then Ebay counts it as a defect.  If you chose Buyer error and the buyer responded agreeing to cancel, then you can contact Ebay and request the removal of the defect.