Follow these instructions and that should solve it:-
You may encounter a message after you have entered your credit card details and pressed BOOK NOW, ¨ technical error ¨ This can mean that the card you have used has not been validated/accepted. But often it can occur if you have been a long time in the booking process or have opened multiple browsers. Shut down all open browsers and clear the cache/history ( if you know how) and start again, preferably using a different browser. If after you have tried this is still does not work, try another card.