Amazon Cognito Error : Unable to resolve host cognito-identity.us-east-1.amazonaws.com

Trying to get CognitoCachingCretdialsProvider (in a Android App) as follows:

public static CognitoCachingCredentialsProvider  getCredentials(Context ctx)
    {
        CognitoCachingCredentialsProvider cognitoProvider = new CognitoCachingCredentialsProvider(
                ctx,
                "us-east-1:xxxxxx-xxxx-xxxx-xxxx-xxxxxxxxx", /* Identity Pool ID */
                Regions.US_EAST_1 /* Region */
            );
        return cognitoProvider;
    }

This Error is shown:

Unable to execute HTTP request: Unable to resolve host "cognito-identity.us-east-1.amazonaws.com": No address associated with hostname
: I/AmazonHttpClient(3427): java.net.UnknownHostException: Unable to resolve host "cognito-identity.us-east-1.amazonaws.com": No address associated with hostname
: I/AmazonHttpClient(3427):     at java.net.InetAddress.lookupHostByName(InetAddress.java:400)
: I/AmazonHttpClient(3427):     at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242)

what could be wrong?