I purchased and registered Studio One 4 Pro in May of this year. When I go to the products page in mypresonus.com and click on the little arrow next to the S1v4Pro registration, there is an green Update button. When I click it, I am asked to enter the new product key. When I copy and paste my existing product key (the only one I have anyway) and press enter, it just keeps asking for the code. Also, there is no choice for me to choose either Presonus Sphere or Studio One 5 Pro.
Safari, iMac running OS X High Sierra