Have you checked your HP Instant Ink account page? Your Instant Ink account page will have notifications if there are any issues with the account or recent cartridge shipment, it will even provide solutions on how to fix the issue. You may log in to your HP Instant Ink account page from here.
To know how to cancel the enrollment, refer to this document.
If the suggested information can't be found, please send us a private message with your Instant Ink account details or you may also respond to the private message I've sent out and I'll help you out, accordingly.