Trying to deauthorize ArcGIS v10.6.1 single use license prior to updating the software to v10.7.1. Deauthorizing software failed error; with this message "Error 7466: The return of this fulfillment is denied by the return policy because max return exceeded."
Software license is current, single use. Windows 10 operating system.
Update: Rename FLEXnet folder to FLEXnet_old in Windows Explorer. Then open ArcGIS Administrator and Authorize Now.
You do not need to deauthorize the Single Use license when upgrading. The same license will apply to the Desktop 10.7.1.
As for the error, there is a limit to the ability to authorize/deauthorize the same entitlement. Like George Thompson mentioned above, contact Customer Service. A representative can reset this on the back end.