External Catalog Setup

I am trying setup an external catalog with one of our vendors who supports the OCI format. I am using AXCI protocol (only choice in the Shopping Protocol drop down) and provided the username and password in the session properties. When I click Validate Settings, I get a "HTTP 400 Bad Request" error. Is there any other setup that we need to do? 

I am using AX 2012 R3.

Thanks