NetWorker Error Message

[Coz]

NetWorker 7.3.2 error message reads: "Cannot create device;storage node enabler required."

This message appears when I try to configure a drive after performing a device scan from networker console. In this setup, I have 6 dedicated storage node licenses. At the first phase, I had 6 storage nodes, 1 networker server with the license manager installed on it. I decommissioned a storage node later at a stage and added another storage node. It seems that one license was consumed by that server which I decommissioned. My question is, how I can make one license reusable after it is already consumed by a server which is not in production.

Thanks in advance.