I want to unsubscribe from the Illustration program, but the Unsubscribe button does not appear.

Moving from forum Community Help to Get Started.

This is a public user-to-user forum.  We can't cancel anything for you but you can.  See link below for details.

https://helpx.adobe.com/manage-account/using/cancel-subscription.html

You have to log into the main Adobe website and then Manage Account button.

You may have to enter your email address and password again, IE your Adobe ID.

Once the next page comes up click on Manage Plan.

Then on the next page click Cancel Plan.

But if your plan has any time left on the subscription period expect to be charged 50% of the remain time period cost for canceling early.