you need Digital account upgrade if your a standard 1.0 account owner. (standard 13 days free)

If you are listed as a standard account owner with only a few days left you might also be using a early access account that will let you register your CE code once it's time is up.

if you are a non-CE 1.0 account owner

You may also have other issues, maybe a invalid code or some other account issue, in that case you will need to contact customer support too.