I have stopped renting out a property where the last guest left early because of an issue. I sent a refund to the guest for the nights not stayed, but because Airbnb only deducts refunds from future payouts, the amount of the refund is sitting in "future payouts" and I am not able to close out my bank account until I resolve this.
I have talked to 2 different people at Airbnb and rec'd no help with this issue.
As Airbnb probably already refunded the guest, it is now only a matter between you and Airbnb.
If they want the money, then i assume they will help you, oherwise this negative amount will remain forever in your Airbnb account. But I noticed you manage 14 listings, so is none of them going to generate a new reservation (payout ?).