This is called "cancelling". However it is not your situation to cancel as a host. The guest must cancel the reservation and work out any details about payment with Airbnb - not you. Under no circumstance should you cancel the reservation. If you get an email that says "are you okay with cancelling" say "no" because this is actually asking you if YOU want to cancel (you do not - you want to get paid so the guest must cancel and pay the penalties not you).
Tell the guest that since the acceptance has already been processed, if they cannot make the commitment to the reservation, they need to cancel.