HI Kuntal,
Which exact version and SP of MII and PCo?
Refer to this SCN article:
in the section ManagementHost Integration with MII, and create A WebService action in an MII transaction, using the same Administrator credentials, and test the GetAgentInstancesRuntimeInfo operation. If this works and returns a response, then you will need to log a ticket against MII for this issue.
Regards, Steve