C# sending Facebook message to myself with FBClient_Simple library not received.

Hi @Gennady Gurin ,

Thank you for confirming. Since FBClient_Simple is the complete implementation used by the application, the next step is to replace the simulated login/send behavior with an implementation that calls Messenger.

The supported flow uses a Facebook Page rather than an email/password login:

1. Connect a Facebook Page to a Meta app.
2. Generate a Page access credential.
3. Have the recipient message the Page first.
4. Obtain the recipient's Page-scoped ID (PSID).
5. Send the response from the Page to that PSID.

First, configure the required values

For a local test, the required values can be kept together:

public static class MessengerSettings
{
    public const string ApiVersion = "v24.0";
    public const string PageId = "YOUR_PAGE_ID";
    public const string PageCredential = "REDACTED";
    public const string RecipientPsid = "YOUR_RECIPIENT_PSID";
}

PageId and PageCredential belong to the Page that sends the message. RecipientPsid is the recipient's ID in the context of that Page; it is not the recipient's profile ID or email address.

For production code, the Page credential should be stored outside the source code.

Next, obtain the recipient PSID

The recipient must first open Messenger and send a message to the Page. If the app has a Messenger webhook, the incoming event contains the PSID as sender.id:

{
  "sender": { "id": "RECIPIENT_PSID" },
  "recipient": { "id": "PAGE_ID" },
  "message": { "text": "Hello" }
}

For a local test, the Page conversations can also be queried using the Page credential in the HTTP Authorization header:

GET https://graph.facebook.com/v24.0/PAGE_ID/conversations?fields=participants
Authorization: Bearer REDACTED

The participant ID that is not the Page ID is the recipient PSID.

Finally, send the message

The following example sends a text message and returns the IDs reported by the API:

using System.Net.Http.Headers;
using System.Net.Http.Json;
using System.Text.Json;
using System.Text.Json.Serialization;

static readonly HttpClient HttpClient = new()
{
    Timeout = TimeSpan.FromSeconds(30)
};

static async Task<SendMessageResult> SendMessageAsync(string text)
{
    string requestUri =
        $"https://graph.facebook.com/{MessengerSettings.ApiVersion}/" +
        $"{MessengerSettings.PageId}/messages";
    using var request = new HttpRequestMessage(
        HttpMethod.Post, requestUri);
    request.Headers.Authorization =
        new AuthenticationHeaderValue(
            "Bearer", MessengerSettings.PageCredential);
    var payload = new
    {
        recipient = new { id = MessengerSettings.RecipientPsid },
        messaging_type = "RESPONSE",
        message = new { text }
    };
    request.Content = JsonContent.Create(payload);
    using HttpResponseMessage response =
        await HttpClient.SendAsync(request);
    string responseBody =
        await response.Content.ReadAsStringAsync();
    if (!response.IsSuccessStatusCode)
    {
        throw new HttpRequestException(
            $"HTTP {(int)response.StatusCode}: {responseBody}");
    }
    return JsonSerializer.Deserialize<SendMessageResult>(responseBody)
        ?? throw new InvalidOperationException(
            "The API returned an empty response.");
}

public sealed record SendMessageResult(
    [property: JsonPropertyName("recipient_id")]
    string RecipientId,

    [property: JsonPropertyName("message_id")]
    string MessageId);

Usage:

SendMessageResult result =
    await SendMessageAsync("Test notification");

Console.WriteLine($"Recipient ID: {result.RecipientId}");
Console.WriteLine($"Message ID: {result.MessageId}");

Here, the message ID is read from the HTTP response rather than generated locally.

In addition, before testing, please confirm that:

• The Page is connected to the Meta app.
• The account managing the Page has the MESSAGING task.
• The app has the pages_messaging permission.
• The Page credential is valid.
• The recipient has messaged the Page first.
• RecipientPsid is the PSID obtained from the webhook or Page conversation.
• The response is sent within the applicable messaging window.
• If the app is still in development mode, the testing accounts satisfy the roles shown in the app dashboard.

The message should appear in Messenger as a conversation with the Facebook Page, not as a personal profile sending a message to itself.

A successful response containing recipient_id and message_id means that the API accepted the request, but it does not by itself guarantee final delivery.

If the message is still not visible, please share the HTTP status and response body after removing the Page credential and personal identifiers.

If you found my response helpful or informative, I would greatly appreciate it if you could follow this guide for your confirmation

Thank you.