External API call is rejected when using gunicorn

[R R]

Hi,

I was using SOAP API successfully on my development machine, and it worked as expected when I was trying out on my VPS. I was using django runserver until this point, but when I ran it with gunicorn, the service started to reject the calls. 

The response is in XML format, but when it's run with gunicorn, the API service sends HTML page saying the service is unavailable. But it works fine while using django builtin server. 

Any idea what might be the reason?

Thanks