DAA assigment error

Hi Experts,

I am trying to assign Diagnostic agent in one system under managed system configuration.Already the DAA is installed in the system and is Registered DAA into Solution Manager SLD & Managed System Configration.Also I am you able to see the SMD agent as green under agent admin in solman workcenter. BUt still I am not able to assign the agent to the system.After giving the assign in assign tab am getting the host agent to assign and after assigning it is showing the below error.

Server name assignment '' on the agent '' failed

Please help.

Thanks,

Arun Raj.