"Invalid JWT Error When Sending Messages from Azure Bot to Skype User

I'm encountering an "Invalid JWT" error when trying to send a non-reply message from an Azure Bot to a Skype user, despite using what appears to be a valid token. Here's a breakdown of my setup:

• I successfully generate an access token using OAuth client credentials for the Microsoft Bot Framework.
• I create a conversation ID successfully, but when I attempt to send a message using this ID, I receive a 401 error with "Invalid JWT."

Here is the relevant part of my code:

import requests

# Setup for token generation

service_url = "https://smba.trafficmanager.net/apis"

token_url = f'https://login.microsoftonline.com/{tenantId}/oauth2/v2.0/token'

token_headers = {'Content-Type': 'application/x-www-form-urlencoded'}

token_payload = {

    'grant_type': 'client_credentials',

    'client_id': app_id,

    'client_secret': app_password,

    'scope': 'https://api.botframework.com/.default'

}

# Token request

token_response = requests.post(token_url, headers=token_headers, data=token_payload)

token = token_response.json()['access_token']

# Setup for creating a conversation

conversation_headers = {'Authorization': f'Bearer {token}', 'Content-Type': 'application/json'}

conversation_url = f"{service_url}/v3/conversations"

conversation_payload = {

    "bot": {"id": f"28:{app_id}", "name": "botname"},

    "isGroup": False,

    "members": [{"id": skype_id, "name": "Milkiyas Gebru"}],

    "topicName": "New Conversation"

}

conversation_response = requests.post(conversation_url, headers=conversation_headers, json=conversation_payload)

conversation_id = conversation_response.json()["id"]

# Setup for sending a message

message_url = f"{service_url}/v3/conversations/{conversation_id}/activities"

message_headers = {'Authorization': f'Bearer {token}', 'Content-Type': 'application/json'}

message_payload = {"type": "message", "text": "My bots reply"}

message_response = requests.post(message_url, headers=message_headers, json=message_payload)

 print("Create Message Response: ", message_response.json(), message_response.status_code)

 The response I get indicates an authorization error:

Create Message Response: {'error': {'code': 'AuthorizationError', 'message': 'Invalid JWT.'}} 401

Has anyone experienced this issue before, or does anyone know what might be causing the JWT to be considered invalid? Any insights or suggestions would be greatly appreciated!