Is the seller located in Canada? If so the seller will be able to send the return label for you.
If the seller is not located in Canada, it's not possible for the seller to issue the return label because the label has to be Canadian.
You've initiated the return and the next step is for you to contact the seller and request funds for the return. You need to use shipping with tracking so likely Tracked Packet unless it's heavier then you might have to use Expedited.. Get the size and weight of the package and go to the CPO website and figure out the cost. Then request that the seller deposit that amount into your paypal account.
After that you just have to wait. If the seller sends the funds return the package.
If the seller doesn't sent the funds escalate the case as soon as they system allows.
eBay will likely put the case on hold for 5 days allowing the seller time to send the funds.
If the seller does not send the funds you will get an automatic refund for your initial payment and no return will be required.
Make sure that the seller does not issue a partial refund for the item but sends actual funds into your PP account. If you paid via PP the seller will have your PP address.
