Access Token And Refresh Token Is Blank

Hi Support Team

I would like to inform you. I'm using box.net API to upload image file but i'm getting issue on API response (access_token and refresh_token is getting blank ).

Errors

Access token is not getting
Refresh token is not getting
Note

These issue is  occurring on my live site ( https://secure.dunnmeadow.com/ ) only and Site is hosted on EC2 amazon server
I have tested on my local server and other server. It's working fine.
Could you help me what i can do.

API Response
===========

Box_API Object
(
[client_id] => hzrzcznrzaeiczf32ym6zw1v4lbtpxbp
[client_secret] => fxdWjUvpigrHUJkW42eqj1idZroqPvAu
[redirect_uri] => https://secure.dunnmeadow.com/example.php
[access_token] =>
[refresh_token] =>
[authorize_url] => https://www.box.com/api/oauth2/authorize
[token_url] => https://www.box.com/api/oauth2/token
[api_url] => https://api.box.com/2.0
[upload_url] => https://upload.box.com/api/2.0
[error_message] =>
[response_status] =>
[asUser] =>
)