Unable to enroll in NSE-2 training

I have completed the NSE-1 training but when I go to enroll in the NSE-2 training I see this message: "You do not have permission to self-enroll." I double checked all the modules for NSE-1 and they are all complete. Anyone know how to get pass this? I have heard that only employees or partners can do the NSE-2 and NSE-3 training. Is this true? Can I then proceed to the NSE-4 studies? I have heard from another source you must complete NSE-1 thru NSE-3 training before moving on to NSE-4. I am very confused. Anybody ever encounter this?