To decommission or reset your Access Controller to factory settings, you'll need to decommission it from Command. This will also allow the controller to be transferred to a new organization.
Site Access Admin for the controller's site
Select Devices in the menu
Click the controller you want to decommission
Select it on the right-hand column
Click the Settings tab
Select Confirm - this cannot be undone
The controller will now reset. Wait 5 minutes before adding the controller to an organization.