If you're trying to log in during early access, you'll get the Subscription error until your early access phase begins
. Product key redemption doesn't actually get recognized by the system yet, according to other posts and tweets from Bioware folks.
In other words, just sit tight and don't worry about that message right now; eventually you'll get into early access, and the subscription stuff doesn't really apply until actual launch day (December 20).
Hope that helps?