What happened at the start of 2017 was that some information was transfered from the old to the current implementation. That meant that account names were reserved, and it was stored which expansions those "old" player had bought. These expansions were free for the old players for one year, though it got extended for a bit IIRC.
So I'm not exactly sure on your status now, do you already have an account made or not? If you do, then nothing more is to be done, the free year that came with your previous purchses is long over. If you don't have an account yet, you likely can get back your old account name (if you tell me your name/email, I can ask the developer to do so). But again, nothing else will be different than making a totally new account.
In other words, the account information was relevant 3-4 years ago, now it is no longer.