The tax is due on the 'consideration' which is defined as
"Consideration" means the consideration charged, whether or not received, for the occupancy in a hotel valued in money whether to be received in money, goods, labor or otherwise, including all receipts, cash, credits, property and services of any kind or nature without any deduction therefrom whatsoever. Nothing in this definition shall be construed to imply that consideration is charged when the space provided to the person is complimentary from the operator and no consideration is charged to or received from any person.
As there is no occupancy for a cover refund surely there will be no tax.
That said if you look on your reservations page and look at cancelled reservations you will now see what Airbnb plan to refund you.