Missing Authentication Token when trying to use ListUsersRequest about aws-sdk-net-extensions-cognito HOT 2 CLOSED

using Amazon.CognitoIdentityProvider;
using Amazon.CognitoIdentityProvider.Model;
using System.Threading.Tasks;

namespace TestConsoleApp_NetFramework
{
    internal class Program
    {
        static string userPoolId = "<<user-pool-id>>";

        static void Main(string[] args)
        {
            string email = "<<valid-email-address>>";
            var response = ListCognitoUsers(userPoolId, email).Result;
        }

        private static async Task<ListUsersResponse> ListCognitoUsers(string userPoolId, string email)
        {
            AmazonCognitoIdentityProviderClient client = new AmazonCognitoIdentityProviderClient(Amazon.RegionEndpoint.USEast2); // Set the region endpoint appropriately.
            var request = new ListUsersRequest() { UserPoolId = userPoolId, Filter = $"email=\"{email}\"" };
            return await client.ListUsersAsync(request);
        }
    }
}