Messaging App Channels API

I’m trying to set up my messaging app. I’ve done authorization and got an object from OAuth (with an access token etc.). Then I’m trying to make a POST request to channels API:

In Headers I’ve added Authorization: {acess_token}

Here is my body:

    "name": {string},
    "provider_channel_id": {string},
    "provider_type": "other"

Here is what I receive:

    "success": false,
    "error": "Failed when querying Provider REST API",
    "error_info": "Please check the reference docs in",
    "data": {
        "reason": "Response code 401 (Unauthorized)",
        "url": "https://{account_name}{provider_channel_id}/conversations"
    "additional_data": {
        "code": "PROVIDER_API_ERROR"

I am creating own app in a sandbox in Developer Hub. I checked the logs, and I received access_token, but even if I immediately fire POST for channels, I’m getting that error.

Also if I go to the Messaging page I will see at the top: {app_name} installation incomplete., but what exactly is incomplete?

What could be the problem? FYI, I’ve followed Messaging app extension


Looks like the auth header is wrong.

It should be like this
Authorization:Bearer {access_token}

Hope it helps!