Change Password using Microsoft Graph Beta

I am using Microsoft Graph beta and trying to reset password for the user..

It is giving me following error

"Exception of type 'Microsoft.Graph.Beta.Models.ODataErrors.ODataError' was thrown.:::: at Microsoft.Kiota.Http.HttpClientLibrary.HttpClientRequestAdapter.ThrowFailedResponse(HttpResponseMessage response, Dictionary2 errorMapping) at Microsoft.Kiota.Http.HttpClientLibrary.HttpClientRequestAdapter.SendAsync[ModelType](RequestInformation requestInfo, ParsableFactory1 factory, IResponseHandler responseHandler, Dictionary`2 errorMapping, CancellationToken cancellationToken)"

My Code

GraphServiceClient _graphClient = GraphHelper.GetAuthenticatedGraphClient(config, credentials);

            try
            {


                await _graphClient.Users[userId].ChangePassword.PostAsync(new Microsoft.Graph.Beta.Users.Item.ChangePassword.ChangePasswordPostRequestBody
                {
                    CurrentPassword = "Password1",
                    NewPassword = "Password2"
                });
            }
            catch(Exception ex)
            {
                Console.WriteLine(ex.Message + "::::" + ex.StackTrace);
            }

public static GraphServiceClient GetAuthenticatedGraphClient(IConfigurationRoot config, B2CCredentials credentials)
        {

            var scopes = new[] { "https://graph.microsoft.com/.default" };

            var options = new TokenCredentialOptions
            {
                AuthorityHost = AzureAuthorityHosts.AzurePublicCloud
            };


            var clientSecretCredential = new ClientSecretCredential(
                credentials.B2CTenantId, credentials.ClientId, credentials.ClientSecret, options);

            var graphClient = new GraphServiceClient(clientSecretCredential, scopes);

            return graphClient;
        }