Why when I add Itunes voucher my account becomes blocked and ask for password change

Hey there Colin,

It sounds like you redeemed a content code, or gift card to your iTunes account but for some reason you got an error message about your account. If the message you received was to due with the account being locked for security purposes then this article has more information on that that means:

If your Apple ID is locked

If your Apple ID is locked for security reasons, you might see one of these alerts:

• “This Apple ID has been disabled for security reasons”
• "You can't sign in because your account was disabled for security reasons"
• "This Apple ID has been locked for security reasons"

When you see one of these alerts, you can go to iforgot.apple.com to unlock your account with your existing password or to reset your password. After multiple unsuccessful attempts to unlock your account, your Apple ID will remain locked and you can try again the next day.

If you use two-step verification, you need to use your recovery key and a trusted device. And if you use two-factor authentication, you need a trusted device or trusted phone number to unlock your Apple ID.

If you see a message that is different from the alerts above and you can't reset your password, contact us for help.

If that is not the error you are getting, can you please elaborate with the exact verbiage of the message you are receiving? Thank you for using Apple Support Communities, all the best!