To cancel a reservation originated on Expedia, you must first check the type of agreement of your listing:

Expedia Collects
Hotel Collects
In this case, your listing is available for package sales and the payment can be processed by Expedia, so to cancel a reservation you will need to contact the Expedia team to explain the case or arrange for your guest to cancel.
It is important to mention that in some cases the cancellation may involve charging the guest or you fees.
In this case, you will be responsible for processing reservation charges, so it is possible to access the extranet and acknowledge the card as invalid within a period of up to 72 hours after the creation of the reservation.
Check the link below for more information from Expedia on the Hotel Collects cancellation routine:

The standard recommendation is not to manually exclude sales channels reservations from Stays, as this generates availability conflicts, but for specific Expedia reasons, in cases of conciliation or no-show, it may be necessary to do the action manually.
For more details on this, click on the link below: