As a banker, I can suggest checking what kind of cards can they accept. Debitcards are definetely accepted, just not all kind. The most problems are with online cards, embossed cards are mostly more well received in american regions (if you have a Maestro card, that might be a problem).
Please make sure Uplay is up to date if going through Uplay and/or using a different browser if online. If you're still getting that error, please reach out to Ubisoft Support and they'll do their best to help you find a solution.