I'm getting this error as well. However, all signs point to it not being an issue in my case. I was able to log in on the ps4 so far and other than some updates it needs to download, I seem to be set up. Even on the Mog Station is no longer shows that I have the ps3 version registered, and my account is active. The code itself seems to be for the game client itself, which #1 is free on PSN and #2 it's registered under my PSN account management.

I think we're ok, but I would still like some kind of confirmation on this.