This is a new security feature to protect your account.
The master password is different from the account password you use to sign in to your account. The Master password controls and limits the functionality of the account.
When you create a master password for the first time, the global settings lock will be activated automatically. You can choose to unlock your account right away reentering the Master password.
Please make sure you remember your Master password and you keep it safe.
If you forget your Master password you need to contact support and you will be asked to prove your identity as legitimate the owner of the account