Facing issue while extending Notification package by adding new workflow

Facing issue while extending Notification package by adding new workflow.

I am trying to extend Notification package by adding new workflow for handling Import OVF as vApp or vApp template in catalog, my new workflow takes following input parameters

            Input              Type

1. vApp               vCloud:VApp
2. vAppTemplate          vCloud:VAppTemplate
3. user                vcloud:User
4. blockingTask                        vCloud:BlockingTask

I created a notification subscription and associate newly developed workflow to it also started subscription listener by executing respective workflows, when I upload OVF for creating vApp from OVF or upload OVF to create vApp template in catalog from VCD. Respective blocking task "vApp Template - Upload vApp Template" initiated and my newly developed workflow get called. Everything seems working except iput parameter user vCloud:User object not found, I compare my workflow with other notification workflows but I could not able to figure it out is wrong or I a m missing.

  Please help me to resolve this issue.

-- AVR