iOS post method is not working in real device

I have created a Ionic 3 Project in windows. Its works perfectly fine in Android. Then I copied the whole folder to Mac for iOS. I removed the plugins and platforms and reinstall it. It works fine as well. But the post Api request working fine in Safari (user agent iPhone) not in a real device(iPhone 6). I use “sudo ionic cordova build ios --buildFlag=-UseModernBuildSystem=0” to build the project.

Can anybody suggest what am I doing wrong?