Try the following steps:
You still seem to have your old Activation Code. Go into your MySteinberg-account and click on “Add software”. Now select “Cubase” and enter your old Activation Code. Afterwards, your old eLicenser should be registered in your account. Click on the eLicensers-tab and select the “Reactivation-button” of the eLicenser. Follow the guide and eventually you will receive your new Activation Code.
Hope that helps.