How to solve "CustomMessage failed with error Cannot read property identity of undefined" error in AWS?

i use aws-sdk for javascript to give user choice to enable/disable 2 factor auth for login. i have 2 issues: UI is capturing user phone and updates cognito phone_number attribute. (updateUserAttributes) First issue is with this stage, it updates the number but returns empty object instead of

{
    "CodeDeliveryDetailsList": [ 
    { 
        "AttributeName": "string",
        "DeliveryMedium": "string",
        "Destination": "string"
    }
    ]
}

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Second, i am trying to send user a verification code with getAttributeVerificationCode with the following payload:

const params = { 
  AccessToken: auth.accessToken,    
  AttributeName: 'phone_number'
}

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and i am getting "CustomMessage failed with error Cannot read property identity of undefined" error. Any ideas?

Thanks