Depending on the code you’re using this could be for a load of reasons.
- It might be expired
- It might only be valid for a certain account (a new or existing one)
- There’s a typo (it might be case sensitive, is it an I or a little L?)
- If it’s none of these things and you still can’t get it to work just drop us a note to firstname.lastname@example.org and we can always double-check the conditions of the code for you!