Deliverr sellers now have up until the order is picked and packed by the fulfillment center(s) to cancel the fulfillment of an order.
How to Cancel an Order
To cancel an order, go to the specific order page for the order you wish to cancel. In the top right of the screen, you will see a "Cancel Order" button. Click this button to cancel the order.
If the order has not already been picked and packed by the fulfillment center, then you will be presented with a pop-up that informs you that your order has been successfully cancelled. 
If the order has already been picked and packed, you will NOT be able to cancel the order and you will be presented with the below message.
Important Reminders
Cancellations are NOT Automatic
Please note that Deliverr does not ingest cancellations from the marketplace nor do we push to the marketplace cancellations that are made in the Seller Portal. If an order is cancelled in the marketplace, sellers must then cancel the order in Deliverr as well.
Similarly, if an order is cancelled in the Deliverr Seller Portal, then sellers must cancel the order in the marketplace. This applies to auto-cancellations that stem from stockouts, international orders that we can't fulfill and mis-linked SKUs. For these cancellation reasons, sellers can expect an email detailing the orders and the reasons why for the cancellations.
Since Deliverr will not push the order cancellation to the marketplace, sellers can also re-route the order to a different fulfillment service in their listing tool / marketplace.
Check Deliverr First Before Responding to Customers
Alternatively, if a customer reaches out requesting to cancel an order, you MUST first check to see if you can cancel the order in your Deliverr Seller Portal before cancelling the order in your marketplace.
If an order is already cancelled in the marketplace and you are not able to cancel the order in your Deliverr Seller Portal, please reach out to the marketplace and/or the customer to come to a resolution that all parties deem appropriate.