@George671
if your guest's plans changed and he wants to cancel then he can cancel and will be refunded according to your cancelation policy. You don't have to do anything.
If you cancel then you will be penalized with 50-100$ fine, you will not be eligible to super host status for a year, those dates will be blocked on your calendar, you will get an automated review that your canceled, your search ranking will suffer and your instant booking option will be turned off. Don't cancel!