The reason is because Individual Edition and Standard Edition are two completely different products.
Individual Edition is an entry level cloud notebook product that is currently going through a sunset process.
Customers who want to keep their data from Individual Edition are required to migrate it to Signals Notebook Standard Edition. Please reach out to your system administrator to find the current Standard Edition tenant for your organization, or contact support if you do not know who your system admin is.
A data transfer process is available for our transitioning customers which is explained in details here.