This error suggests that there is a mistake or something wrong with the address.
Please go to your address book, delete the address of the item you're trying to send and add it again.
To delete an address from your Touchnote address book, please firstly go to the 'more' section of the app and choose the address book tab. Once there, you should see a list of all your addresses presented with an 'edit' option next to them. Simply click on the 'edit' button and you will be given an option to delete the address at the bottom.
Please make sure all the mandatory fields, including the postcode, are filled out.
Once the new address is saved, try sending the card again and it should work out this time :)