If you do not have a valid address the seller MAY cancel the order on the basis of a bad address. OR the seller could ship it and then a whole can of worms is opened. If it get delivered to a wrong address and the tracking shows the item was delivered then the seller is off the hook. If it is a bad address, item will get sent back to the seller & the seller will cancel order for undeliverable.
You have to have the correct address when you make the order - seller if he/she wants to be protected HAS TO ship to the address on the order. So changing and address after you purchased will have no effect.
Perhaps you can ask the seller, if they haven't shipped yet, to cancel the order at your request? Then ask the seller to relist the item and you can then go buy it with the correct address. er, that is IF the seller still wishes to fool with you and hasn't added you to their blocked buyer's list.
You may also wish to go into your "My eBay" and look through your account, there are several places where your address is stored and one may need to make updates in each location. Also don't forget to change your address in PayPal too.
Good luck!
