AWS Cognito Android - Internal error checking call api attribute

Question

AWS Cognito Android - Internal error checking call api attribute

I have successfully integrated AWS Cognito features into an Android app using compile 'com.amazonaws:aws-android-sdk-cognitoidentityprovider:2.4.6'

The SignUp and Login functions work fine, but when I try to validate an attribute phone_number, it gives Internal error.

What I've done

Step 1: Get a Confirmation Code for the Attribute phone_number

user.getAttributeVerificationCodeInBackground("phone_number", new VerificationHandler() {
            @Override
            public void onSuccess(CognitoUserCodeDeliveryDetails verificationCodeDeliveryMedium) {

            }

            @Override
            public void onFailure(Exception exception) {
                LogHelper.printErrorLog(dataManager.formatException(exception));
            }
        });

and I get a confirmation code on my mobile phone as sms with a 6-digit code.

Step 2: Submit Verification Code

user.verifyAttribute("phone_number", verificationCode, new GenericHandler() {
            @Override
            public void onSuccess() {

            }
            @Override
            public void onFailure(Exception exception) {
                LogHelper.printErrorLog(dataManager.formatException(exception));
                // here i am getting Internal Error
            }
        });