Saying I need a pre-order code for early access as a Legacy player.

[Nekodar]

I do hope this is the case because when I start up the client, it says there is no valid service account. Maybe it's only referring to the early access and I'll get a different message once release starts?

It's possible that they are restricting it now due to the load expected from players that do have early access.
A response from rep/dev would help to clear things up though.