Once a service is cancelled from the Services tab by clicking on the "x" on the right side of the page in the "Actions" column the cancelled service will moved to Archived Services.
If needed, cancelled services can be restored from the Scheduling -> Archived Services page. To restore a cancelled service search for the customer or service, on the Archived Services page, and then select it on the left side of the page. Then click on the "Restore Services" button at the top of the page.
Once the service is restored it will show on the Services tab again but it will show as cancelled. To undo the cancellation click on the undo icon on the right side of the page in the "Actions" column.
Last click on the "Restore" button to restore it. If you want to send a restoration email to the customer (optional) you can select that option.
Once the service is restored it will show as "Pending" once again on the "Services" tab and it can be scheduled from the Unassigned Services page.