How do I unlock my iCloud account?

To unlock your iCloud account, visit iforgot.apple.com and follow the steps to reset your password. You may need to verify your identity with security questions, email, or two-factor authentication. If you're still unable to access it, contact Apple Support for further assistance.

Most common reason is that your password has been entered incorrectly too many times. This protects your account from someone trying to guess your password and also brute force attacks from automated bots. Review this link for additional information and the steps to take to reset your password.

If your Apple Account is locked, not active, or disabled - Apple Support