Saving data into dynamodb using unauthenticated arn from android doesn't work

I am trying to save a test record to amazon dynamodb table from Android.

    Context mContext = this.getApplicationContext();

    CognitoCachingCredentialsProvider cognitoProvider = new CognitoCachingCredentialsProvider(
            mContext, // get the context for the current activity
            "xxxxxxxxxxxxxx",
            "us-east-1:dsfhjhsd-sdfsfds-sdffds-dsffs",
            "arn:aws:iam::7777777777:role/Cognito_CustMobAnalyticsUnauth_DefaultRole",
            "YOUR AUTHENTICATED ARN HERE",
            Regions.US_EAST_1
    );

    try {

        AmazonDynamoDBClient ddb = new AmazonDynamoDBClient(cognitoProvider);
        //ddb.setRegion(Region.getRegion(Regions.US_EAST_1));
        DynamoDBMapper mapper = new DynamoDBMapper(ddb);

        androTest mytest = new androTest();
        mytest.setMyKey("testKey-1");

        try {
            mapper.save(mytest);

        } catch (AmazonServiceException ex) {
            Log.e("CustomError", "---> " + ex.getLocalizedMessage());
        }
    } catch (Exception e) {
        // This will catch any exception, because they are all descended from Exception
        Log.e("CustomError", "---> " + e.getLocalizedMessage());
        Log.e("CustomError", "---> " + e.getMessage());
    }

I am getting the following message while executing and data is not updated. I am using unauthenticated arn.

 D/CognitoCachingCredentialsProvider﹕ Loading credentials from SharedPreferences
 D/CognitoCachingCredentialsProvider﹕ No valid credentials found in SharedPreferences
 E/CustomError﹕ ---> null
 E/CustomError﹕ ---> null

Following is the role policies

{
"Version": "2012-10-17",
"Statement":[{
    "Effect":"Allow",
    "Action":"cognito-sync:*",
    "Resource":["*"]
    }]
}

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "Stmtxxxxxx",
      "Effect": "Allow",
      "Action": [
        "dynamodb:DeleteItem",
        "dynamodb:DescribeTable",
        "dynamodb:GetItem",
        "dynamodb:PutItem",
        "dynamodb:Query",
        "dynamodb:Scan",
        "dynamodb:UpdateItem",
        "dynamodb:UpdateTable"
      ],
      "Resource": [
        "arn:aws:dynamodb:us-east-1:663633636363:table/androTest"
      ]
    }
  ]
}

Following is the trust policy

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "",
      "Effect": "Allow",
      "Principal": {
        "Federated": "cognito-identity.amazonaws.com"
      },
      "Action": "sts:AssumeRoleWithWebIdentity",
      "Condition": {
        "StringEquals": {
          "cognito-identity.amazonaws.com:aud": "us-east-1:chgsdhg0-sdds-sdsd-7687668c05"
        },
        "ForAnyValue:StringLike": {
          "cognito-identity.amazonaws.com:amr": "unauthenticated"
        }
      }
    }
  ]
}