Unfortunately with a generic error message like that, it could be almost anything.
Are you able to print a label using a different service such as PayPal or Pirate Ship? That might be a workaround or at least generate a more useful error message if there is a problem with the address.
See this thread for some possible things to check or workarounds to try:
Ive tried all. Ebay ended PayPal communication. I think I may have to end shipping internationally. The only solution I can come up with is to purchase through USPS first class and lose money. Thanks for trying.
