Hopefully you have the guest response confirming the intent to cancel on the Air BNB message system. Then contact Air BNB directly, requesting a non-penalty cancellation based on the guest stated intention. Alternatively, the guest might be waiting for Air BNB to allow full refund cancellations, including the Air BNB fee. You could offer to refund the amount of the Air BNB fee IF the guest cancels within 24 hours. That will open your calendar and the guest will get the full refund. If you have other guests interested, you will ultimately have better guests than the current ones that are willing to hang you out to dry for their own benefit.