Error message in HU02

Hi Experts,

I am getting error mesage "HU functions outside of the delivery only via unique number assignment" when Enter HU02.

I tried to activate the Unique number assignment in Config via SPRO--> Logistics general --> HU --> External Identification --> Set unique number assignment and got the error message below.

"HU lean status update is active, unique HU numbering not possible'

Please help me to overcome this Issue.