Unauthenticated access is not supported for this identity pool, while using DynamoDB

I am exploring AWS for iOS,

I am trying to use following things,
1.DynamoDB
2.Cognito
3.Facebook LogIn

I was getting AWS DynamoDB scan working when there wasn't any LogIn integrated. After integration LogIn with Facebook, I am configuring facebook to cognito like this:

 if let fbToken = FBSDKAccessToken.currentAccessToken().tokenString{
        let credentialsProvider = AWSCognitoCredentialsProvider(
        regionType: CognitoRegionType,
        identityPoolId: CognitoIdentityPoolId)
        credentialsProvider.logins = [AWSCognitoLoginProviderKey.Facebook.rawValue: fbToken]
 }

But after configuring this I don't have access of DynamoDB now. It says: Unauthenticated access is not supported for this identity pool

Note: LogIn is necessary in my case.