Thanks guys, I did engage elastic support couple weeks ago but because it's not a Sev 1 the response time is usually much slower than what's needed esp. when am trying things. This forum is surely much quicker to respond and so thought of trying it out here.
@zx8086: FYI - this is an in-house S3 compatible storage (not AWS cloud) and so am using what our system admins provided me to connect to it. It works when tried using aws cli from the same elastic node.