External login not working Identity server 4 asp.net core

External service configuration not working with identity server 4.

public static void ConfigureExternalOidcProvider(this IServiceCollection services)
        {
            services.AddAuthentication().AddGoogle("Google", options =>
            {
                options.SignInScheme = IdentityServerConstants.ExternalCookieAuthenticationScheme;

                options.ClientId = "xxxxxxxxxxx-xxxxxxxxxxxxxxxxxx.apps.googleusercontent.com";
                options.ClientSecret = "xxxxxxxxxxxxxxx";
            }).AddFacebook(options =>
            {
                options.SignInScheme = IdentityServerConstants.ExternalCookieAuthenticationScheme;
                options.AppId = "xxxxxxxxxxxxx";
                options.AppSecret = "xxxxxxxxxxxxxxxxxxx";
            });
        }

In the external controller, the schema is null, but I hardcoded the schema with IdentityServerConstants.ExternalCookieAuthenticationScheme even though it is not working.

public IActionResult Challenge(string scheme, string returnUrl)
    {
        if (string.IsNullOrEmpty(returnUrl)) returnUrl = "~/";

        // validate returnUrl - either it is a valid OIDC URL or back to a local page
        if (Url.IsLocalUrl(returnUrl) == false && _interaction.IsValidReturnUrl(returnUrl) == false)
        {
            // user might have clicked on a malicious link - should be logged
            throw new Exception("invalid return URL");
        }
        
        // start challenge and roundtrip the return URL and scheme 
        var props = new AuthenticationProperties
        {
            RedirectUri = Url.Action(nameof(Callback)), 
            Items =
            {
                { "returnUrl", returnUrl }, 
                { "scheme", scheme },
            }
        };

        return Challenge(props, scheme);
        
    }

When I click on the Google and facebook button it, never redirects to the google or facebook page.

Here is the result from my debug option

Google click

Facebook click

CSHTML code

   @if (Model.VisibleExternalProviders.Any())
                    {
                        @foreach (var provider in Model.VisibleExternalProviders)
                        {
                            <a class="@($"mdc-button mdc-button--outlined ml-1 mb-1 {(provider.AuthenticationScheme == "Google" ? "mdl-button--googleplus google-logo" : "mdl-button--facebook")}")"
                               asp-controller="External"
                               asp-action="Challenge"
                               asp-route-provider="@provider.AuthenticationScheme"
                               asp-route-returnUrl="@Model.ReturnUrl">
                                @if (provider.AuthenticationScheme == "Google")
                                {
                                    <i class="fab fa-google fa-fw google-logo"></i>
                                }
                                else
                                {
                                    <i class="fab fa-facebook-square fa-fw"></i>
                                }
                                @provider.DisplayName
                            </a>
                        }
                    }

Answers:

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Method 1

Without further information it is hard to answer your question, so I am going to start, and then improve on my answer as you give more details. First of all verify that you see a scheme query parameter when hovering over the external login button:

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