Getting null response from api in test flight version only, response contains zip folder with images

Hi Team,

I am facing below issue in TestFlight version (IOS) only.

My requirment is to fetch zip folder(Zip folder contains all images) from api and display it.
The problem here is whenever I upload my application on TestFlight I am getting null in api response and if I create normal diawi link then I am getting the zip folder in response.

Any idea why I am not getting api response having images zip folder in test-flight version?

P.S : That api also contains custom headers.