[FJames]

Try calling your credit card company. I've done that before when payment wasn't authorized for an online purchase, and they were able to tell me exactly what was wrong with the transaction (e.g., wrong expiry date given, wrong address etc.). Then you can go back to Kobo customer service armed with more precise knowledge about why the transaction isn't going through successfully. If you entered something incorrectly on the initial attempt, it might be cached somewhere even if you have corrected it subsequently, or they might have temporarily blocked subsequent transactions from the same source after the initial failure (and they don't always tell you that).