@Eugénie3
If a card is not accepted/not going through, there is a reason. It could be a stolen card, the credit could be maxed out, card is expired. Or the potential guests are scammers trying to lure into accepting payment outside airbnb, pretending the card payment does not go through.
If they try to book and there are issues with the card, you will get a message through the airbnb system that there are payment issues and a time frame for the issue to be resolved. If not resolved, the request would be cancelled automatically.
If the card is rejected. there is a very good reason.