Why Agent is not installed on UD agent even Install UD agent job showing successful

Hi All, We are running the Infrastructure discovery in our Production instance and activity completed with mixed results like successful, warnings and errors. And Inventory discovery is running on the records which are successful in Infrastructure activity and Inventory discovery compelled for some of the records. But after some time we came to know that UD Agent is not installed in the Nodes and we cross verified in UDA CI type. We found zero records in UDA CI type. It would be helpful for us if anyone suggest us how to trouble shoot and how to find the reasons for why UDA agent is not installed on the machines and why In Infrastructure activity showing successfully even agent is not installed. Thanks, Swamy