Your SE account has to be active, with only the characters deactivated from lack of payment. I'm surprised that it only has to be 2 days, I thought they would want 45 days for something like this.
I had been using crysta when I stopped playing years ago, all I had to do was stop feeding in crysta to be ready for free campaign to kick in. Maybe if you were using direct credit card billing there is a wrong way to cancel that turns off your SE account.
I’ll try logging in later then. The instructions on the SE site said to select the account to reactivate, then select the chars to reactivate, when I did this it wanted me to enter payment.