Auth0 management API CreateAsync returning internal server error (500)

In the online managament API from Auth0 i can create a user with this body. But here somehow the CreateAsync is not working.

private async Task CreateUserAuth0()
        {
            var newRequest = new Auth0.ManagementApi.Models.UserCreateRequest
            {
                Connection = "Username - Password - Authentication",
                Email = "update2@update.com",
                Password = "Test123456"
            };
            var response =  await _managementApiClient.Users.CreateAsync(newRequest);
        }

The Update and Delete calls are working fine.

private async Task UpdateUserEmailAuth(string email, string newEmail)
        {
            Auth0.ManagementApi.Models.User user = await GetUserAuth0(email);
            await _managementApiClient.Users.UpdateAsync(user.UserId, new 
                             Auth0.ManagementApi.Models.UserUpdateRequest
            {
                Email = newEmail
            });
        }
        private async Task UpdateUserPasswordAuth(string email, string password)
        {
            Auth0.ManagementApi.Models.User user = await GetUserAuth0(email);
            await _managementApiClient.Users.UpdateAsync(user.UserId, new 
                      Auth0.ManagementApi.Models.UserUpdateRequest
            {
                Password = password
            });
        }
        private async Task DeleteUserAuth0(string email)
        {
            Auth0.ManagementApi.Models.User user = await GetUserAuth0(email);
            await _managementApiClient.Users.DeleteAsync(user.UserId);

        }