Whenever possible, do not cancel the reservation from the owner/operator side. If the owner/operator cancels the reservation, it will result in negative online reviews from travelers, which will negatively affect the overall visibility of the property on vacation rental portals.
If you know for sure that you will not be able to accept a reservation for a sudden reason, you should cancel the reservation as soon as possible. For example, canceling a reservation 24 hours after it has been accepted risks negatively impacting the traveler and leading to lower online reviews.
If you are unable to operate and manage your vacation rental property for more than 24 hours, mark it as temporarily unavailable for reservation. This will prevent you from receiving requests for reservations that you cannot handle operating and managing.