Workflow is not going into Activity Step

Hi Expert,

I'm trying to trigger a worflow like below.

I have given all the required screen shots. But I can see that activity step is not triggering but at the same time the mail step trigger successfully.

This workflow is being triggerred from our custom program like below ..

Am i missing something .. pls help me.

Activity step:

Object and method assignment in activity step:

All the Object type and method are in place.