The Sub-Password system enables you to increase your accounts protection by creating a four digit password for your character, equipment and storage. Enabling these passwords is optional, but will offer you increased peace of mind, because even if someone does gain access to your account they will be unable to access your precious equipment.
If a sub-password is incorrectly typed five times the account will be locked.

Unblocking an account that has been locked
1) Sign-In to the website
2) Go to "Account Management" section.
3) Click on OTP button to send the OTP to your registered email account.
4) Type in your OTP sent to your email on the blank space provided.
5) Your account is now unblocked from Sub-Password block and Sub-Password is reset

Yea..it says that...I do that, Wheres the OTP? -.-