Opening authenticated image via API

Our Zendesk application connected to Twitter and sometimes our customer send image via Twitter DM. In Zendesk the image url will be shown as https://{subdomain}.zendesk.com/twitter/proxy/authenticated_image?conversion_id_str={conv_id}

We try to get the image by API call (to automate things). We already use Basic Authentication with user and password. But we always get this response saying that we are unauthenticated. If we try it in browser, we are able to open the image. Do you have solution for this Zendesk team? Thanks