Error Encountered with Teams Incoming Webhook: Missing CreatedByObjectId

While testing a Teams incoming webhook URL, the following error occurs despite receiving a status code of 200:

System.ArgumentNullException: Value cannot be null. (Parameter 'CreatedByObjectId cannot be null or empty')

This parameter was not an issue last week. Is there documentation available that explains this API?

import requests
import json

url = "Webhook URL" 

data = {
    "message": "Hello, this is a test message!",
    "summary": "test summary",
    "text": "test text from example_post.py",
}

headers = {
    "Content-Type": "application/json"  # Ensure it is set to send JSON data
}

response = requests.post(url, data=json.dumps(data), headers=headers)

if response.status_code == 200:
    print("Response status code:", response.status_code)
    print("Response text:", response.text)
else:
    print("Response status code:", response.status_code)