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?