Can you double check the alias that you are using? In my org, we use what would be the exchange alias in AD which is first initial and first 7 characters of the last name. And also make sure that you entered something in the password field- Advanced UM on Nupoint will use the exchange super user but the actual mailbox will never enable unless you 1- change the FAC to Adv UM and 2- enter the correct alias and enter something in the password field. There is a command that you can enter if you putty into the Nupoint, as root, that will allow you to monitor real-time exchange activity such as mailbox initialization, etc.
