@Olivia-P0
Have you already explained to your guest?... are they understanding and able to re-accomodate?
If you have, then you can ask for a payout refund to be made to the guest, as agreed with your guest.
Depending on the guest situation, you may need to find and pay for the alternative accomodation for them, so that they are not left "stranded" by the unfortunate situation.Have you reached out to the guest in terms of finding an alternative...should that be necessary? Ring AIRBNB and explain your situation,after obviously discussing with your guest, what their situation is.