To unassign a license, perform the following steps:
Go to Manager → <Admin Domain Name> → Setup → Licenses.
Click the System tab.
Select the license you wish to unassign.

Click Unassign.
Click Ok.

Note
The Licenses page allows you to perform single license unassignment for NS9600 Sensors. Use the Manager → <Admin Domain Name> → Global → Device Manager page, if you want to unassign multiple licenses at once.
Once a license is unassigned from a Sensor, the Manager will not be able to deploy pending changes, including new signature sets and policy updates to the Sensor.