Minimal Requirements to Access OneFS API

Hi folks, we have a customer having trouble accessing their Isilon OneFS API through our software. We keep getting bad user name or password as an error.  They are even trying the root user with no luck. That same user can login to the web admin interface using the same credentials. The first thing we do is create a session according the API doc.

If we deploy a simulator out of the box, using the root user and what ever password at cluster creation time, our product has no problem. But our customers are frequently having problems with this.  Are there some settings that restrict access to the API?  What should I be looking for?

Edit: I just realized something, when we send the POST request to  "/session/1/session" we actually send BOTH platform AND namespace as services.  Could it be that we don't have namespace privilege and thus can't get a session cookie? I will test this theory.