I don't think the Creative Cloud doesn't come with an Adobe Sign subscription. An Acrobat subscription comes with an Adobe Sign subscription, but even that my not be anything more then sending documents from with Acrobat for signing, not from within Word.
I have checked your account with the email address used by you to sign-in to the forums. You have subscribed to the Adobe Creative Cloud all apps for Education which do not includes the cloud services. That means the Adobe Sign service is not included in your service.
You have an Adobe Sign trial account registered with the same email address that is the reason it shows that message.
If you are using an alternate email address for the service, please share the email address in private message.