@Dan107....Hi Dan, As I understand from your question you HAVE already accepted this booking so the 24hr rule does not apply on your side and if payment is not made by the guest Airbnb will cancel the booking without any further intervention from you!
Should you want to talk to someone there is a phone number for Austria and it as follows...
Austria / Österreich: +43 72 08 83 800. This number is of course an international number. Being a local you would know to drop the prefix.
Dan, don't ever cancel a guest booking request that you have accepted yourself! Always call Airbnb and ask them to instruct the guest to cancel the booking, or else have them cancel the booking on behalf of the guest.
Dan, this is most important, and do not let Airbnb ask you to accept the cancellation for the guest....You will be heavily penalised if you do. Explain that you were and are prepared to host the guest and any cancellation will have to be on the guests side. Many hosts have been 'tricked' by Airbnb help desk into accepting responsibility for cancelling and the automated system does not take into account circumstances, it only recognises who cancelled.
Sorry to labour a point there but you need to be very clear about this.
Cheers....Rob