Need access back for keychain on all devices. New iphone setup is asking for a passcode that doesn't exist. When you link new iphone/ipad to old apple id which already linked to several idevice, you may be asked to enter passcode for other iphone, just enter the apple id linked idevice screen password to bypass this notice on new iphone/ipad.
If you forgot the passcode or the verification keeps failing, this article can help you. If you use ios 11.3 or later on your iphone, you might not need to enter a verification code. When setting up your new iphone or updating apple id information on your device, you might encounter the enter passcode for other iphone screen.
Locked out of your iphone and forgot your passcode? The easiest way to reset your password is with your iphone or other trusted apple device — one that’s already signed in to your apple account, so that apple knows that it’s yours. Learn how to reset your apple id password on a trusted device or through the apple support app on a family member’s iphone, ipad, or ipod touch. Use a computer to put your iphone into recovery mode so you can erase your phone and set it up again.
You’ll need to trust the device by entering the verification code from.