The Assign Storage Unit task has not completed because the storage unit that you have attempted to assign is already assigned to another storage complex. The storage unit has the correct authentication key for the storage complex to which you have attempted to reassign it. If you click OK to force the assignment of the storage unit to the storage complex that you specified, the storage unit is unassigned from the storage complex to which it is currently assigned.
Click OK to force the assignment of the storage unit to the storage complex that you specified. Click Cancel to cancel the operation without changing the assignment of the storage unit.