When you tap the Grownups/Settings section and view the Account menu, what do you see? If you are signed in and see Monthly/Annual then you are subscribed to the service.
If you see Not Subscribed listed under the Subscription option,
then you are not subscribed to Noggin or your account is not linked to your subscription. You can choose the Subscribe option to start your free trial/subscription or restore your current subscription if you are on the same device where you subscribed to Noggin.