I have no "organization" associated with my "ArcGIS Online" account. Esri sent me an email with the following:
"To activate your subscription, click the following link or copy it into your browser: https://www.arcgis.com/home/signin.html?activationcode=XXXXXXXXXXX".
I click on the link and it takes me to my sign in page. When I enter my username and password, I get this error: "Cannot add user to subscription. Items and Groups cannot be moved into this type of subscription."