Hi, im hitting this problem when tring to create a trial account. I successfully register stormblood and sub with mogstation around early of june, no problem too.
After my research, SE start to blacklist IP over the world when login with EU/US account, a lot VPN IP being block too. You can still play the game if you have sub, if you want to sub or buy from mogstation, or register for a trial, you will hit this problem if your IP is blacklisted.