This error is typically caused by one of two issues.
To address this issue, please ensure that you have enabled both "Allow Force Reservation" and "Allow Force Release" in the Avalanche GUI under Tools>preferences>port administration>reservation menu. Once this is done, please try forcing the other user off. You can also try rebooting the appliance/card.
To address this issue, please ensure the s/w that is being used on the chassis and in the Avalanche GUI match. If they do not, it is recommended that you download the current GA build from the Spirent Support Site ( support.spirentcom.com).