This issue was resolved. I was placing the secret key at wrong place.

It is the same thing with my app too..They had been continuously rejecting my app. I request for a call, the reviewer never responds. I gave them recording of that things are working in testFlight, snapshots, wordings, etc, but it is like if they have decided to reject your app, even God cannot get it passed. You are just at the mercy of their team. They simply come online, login, find some or other issue and reject the app. It is a sorry state of affair. Explanations for Rejections are 1 liners, often snapshots associated are not linked to the points raised in rejection. I have also decided, I will keep on submitting the app without making changes, if they cannot give right information and snapshot, then I cannot make any changes. It is a nightmare.

Hi Team, The issue is resolved, I guess the reviewer understood what I was trying to explain and has approved the app now.