This message refers to your PacKit account. You can register forever with a free account if you only use the free features, or buy a Plus subscription if you need more.
The option to log in into your PacKit account is found in the first tab, next to your your Intune log in options. You can sign up on this page if you just want to create a free account:
When you purchase a Plus subscription, an account is automatically created for the email address you specify on the checkout page.