Getting error "an ssl error has occurred and a secure connection to the server cannot be made" with test flight build.

I would like to update my problem to elaborate more.

I generated IPA targeting iOS 11 and uploaded to test flight. I don't receive this error while trying to connect to web server with https url. This issue is happening only with IPA generated using iOS 12. My code base uses Xamarin.iOS but still the httpclient implementation uses NSUrlSessionHandler which is xamarin's implementation to use NSUrlSession underline.

Any help is highly appreciated.