GA4 measurement protocol event attribution, not working with event one week later?

Question

I have GA4 running on my site, and in my backend I store the user's client_id and session_id. With measurement protocol on our backend, I send a custom trial started event when a user starts their trial, and I send a custom subscription paid event when a user pays for a full month. Both of these events use the same function in my code, so I know nothing is shifting between them:

# sends google analytics event
def send_ga4_event(event_name, customer_id):
    measurement_id = os.getenv("GA_MEASUREMENT_ID")
    api_secret = os.getenv("GA_MP_SECRET")
    ga_debug_mode = os.getenv("GA_DEBUG_MODE") == "true"

    user = get_user(stripe_id=customer_id, tag="send_ga4_event")
    if not user:
        logging.warn("send_ga4_event: User doesn't exist in database")
        return False
    elif not user.stripe_email:
        logging.warn("send_ga4_event: No stripe email associated with user")
        return False
    elif not user.ga_client_id:
        logging.warn("send_ga4_event: No ga_client_id associated with user")
        return False

    if not user.ga_session_id:
        logging.warn("send_ga4_event: No ga session id associated with user, continuing anyway.")
    """Send an event to GA4 with a hashed email."""
    hashed_email = hashlib.sha256(user.stripe_email.lower().encode()).hexdigest()
    params = {"debug_mode": ga_debug_mode}

    if user.ga_session_id:
        # logging.debug(f"send_ga4_event: USER {user}")
        params["session_id"] = user.ga_session_id

    event_data = {
        "client_id": user.ga_client_id,
        "user_id": hashed_email,
        "non_personalized_ads": False,
        "events": [{"name": event_name, "params": params}],
    }
    headers = {"Content-Type": "application/json"}
    url = f"https://www.google-analytics.com/mp/collect?measurement_id={measurement_id}&api_secret={api_secret}"

    response = requests.post(url, headers=headers, data=json.dumps(event_data))
    if response.ok:
        logging.debug(
            f"send_ga4_event: event_name {event_name}, customer_id {customer_id}, email {hashed_email}, measure id {measurement_id}, api secret {api_secret} [{response.status_code}, {response.text}]"
        )
        return True
    else:
        logging.error(
            f"send_ga4_event: event_name {event_name}, customer_id {customer_id}, email {hashed_email}, measure id {measurement_id}, api secret {api_secret} [{response.status_code}, {response.text}]"
        )
        return False

When I say attribution isn't correct, I mean the subscription paid event shows up in the traffic report on GA4 as 'unassigned'. This issue originally happened for trial started events too, but once I added session_id to the events, it attributed correctly.

In the data being sent, I send their client_id, user_id (which is their email hashed), and inside 'events' i send 'session_id'.

From reading the docs, I was under the impression I should be updating the session_id and client_id stored in our backend every time it's changed on their browser. The docs sound like it should connect any sessions that go back 90 days. The time between a trial start and a subscription paid is one week, so this shouldn't be an issue.

Has anyone experienced this? if so, how do you fix it?

Answer 1

Events can be sent for sessions that have expired, but session-related metrics will show as “not set” in GA4, even though they are present in BigQuery.

Submitting an event for a session that ended, say, more than 3 days ago, while it counts towards total events and appears in BigQuery, will reflect “not set” for metrics like landing page and session source/medium in GA4 reports. This is because sessions can not accept new events after they have expired.

also you can check other issues related to attribution not working in this medium : https://medium.com/@aliiz/navigating-measurement-protocol-challenges-and-eliminating-not-set-issues-in-ga4-a-technical-7f01863649d6