@Alison91
The guest had to cancel the reservation on the same day he informed you of not being able to travel.
Then the cancellation policy will automatically calculate the refund (if any). If the policy was "strict", only cleaning fee (if any) will be refunded, as cancellation is just 4 days before check-in.
The special "COVID extenuating circumstances" policy does not apply, as travel issues are excluded from having a refund.
You can decide to manually gve the guest some refund, but at least the reservation must be cancelled first (by the guest !) to continue and free up the days on the calender for other booking.