Windows Phone 8.1 WWW post request error

Hi guys,

I'm currently working on a game on the 3 mobile platform, which are Android, iOS and WP8.1.

The Android and iOS version are almost done but there is an issue with the WP8.1.

In the game I do some POST json request using the WWW class in the Unity for the player to login. The POST request is working fine on both Android and iOS which the player able to login and server will return the login success message back to player.

But then the same code is not working on WP8.1. When I deploy the game to an actual Windows Phone, the POST request is not working and returning "Error 400" but the GET request is working just fine. On top of that, the same code that was not working when running on actual device is working when using Unity Editor. When run using Unity Editor, the GET and POST request are working just fine.

Currently using Unity 5.1.1f1

Any guideline or suggestion will be appreciate.

Thanks