Pradeep,
I'm not sure what's going on with your implementation, but I've attached a doc I just put together that's as close to a step-by-step configuration as I can get at the moment. It starts with the actual enablement of the API. Please go through and verify every step even if you know you've already performed them.
Once you've verified every step, try the skill again, but start with the most basic action which is
drive.about.get.
Cheers,
------------------------------
Eric Wilson
Director, Partner Integrations for Digital Exchange
Blue Prism
------------------------------