@Sherry229 It was up to your son to cancel the booking, not the host. If he had cancelled within 48 hours, he would have received a full refund. The refund would have been issued by Airbnb, not the host. Hosts receive serious penalties from Airbnb for cancelling reservations, and they would only do so if it was a host issue that they had to cancel, not a guest issue.
And at this point, the host doesn't have the $ for the reservation, Airbnb does. Hosts don't get paid until 24 hours after a guest checks in.
So yur son needs to contact Airbnb, explain what happened, and find out how to proceed. If he hasn't cancelled this reservation, the host's calendar is still blocked for these dates. So no one else can book them. Hosts are often willing to refund a guest (which may be the only option now, as your son missed the free cancellation window) if they are able to rebook those dates, which they can't do until your son cancels.