Not able to purchase Mathcad Prime Student Version

I am a student and want to purchase the Mathcad Prime 10 Student version (the one for $63/year), but when I click on the link that says "Order Now", it just brings me to the "Mathcad Express Free Download", which is not what I want. I already have Mathcad Express, and I wish to purchase the student version for $63/year, because I am a student who needs Mathcad Prime. In other words, I have found no way to actually purchase/buy the student version of Mathcad Prime. Is there any fix to this to allow me to buy the student version?