Fix GA4, GTM and Cookie Consent Tracking Issues

Freelance Job: GA4 / GTM / Cookie Consent Tracking Expert
Project Overview
We are looking for an experienced GA4, Google Tag Manager (GTM), and Cookie Consent / Consent Mode specialist to investigate and resolve a significant analytics tracking issue on a production website.

The website recently moved from a cookie opt-out model to an opt-in consent model. Following this change, we observed an approximately 97% drop in traffic visibility across GA4 and another analytics platform.

We need an expert to identify the root cause, implement the appropriate solution, and validate the tracking end-to-end.

Current Findings
Our initial investigation has identified the following:

The website uses Cookiebot as the Consent Management Platform (CMP).
GTM is currently conditionally loaded based on cookie consent.
The GTM container is currently implemented with:
type="text/plain"
data-cookieconsent="statistics"
Google Consent Mode is also implemented on the website.
After users provide consent, GA4 page_view requests are successfully generated.
The GA4 request contains the complete landing-page URL, including UTM parameters.
UTM parameters are therefore not being stripped from the URL.
Testing indicates that users who consent can generate GA4 events successfully.
However, users who have not consented may receive no analytics signals at all.
Cookiebot support has indicated that the GTM container is being blocked at the container level and recommended allowing GTM to load before consent, with consent controls handled within GTM/Consent Mode.
Their recommendation also includes removing the invalid data-cookieconsent="necessary" attribute from the Google Consent Mode implementation.
The implementation team has confirmed that Advanced Google Consent Mode v2 is not currently configured to allow GA4 cookieless signals from non-consenting users.
Primary Problem

We need to determine whether the current CMP + GTM + Google Consent Mode implementation is preventing GA4 from receiving privacy-preserving signals before consent and therefore causing the large traffic/measurement drop.

Scope of Work
The freelancer should:
Audit the current Cookiebot + GTM + GA4 implementation.
Review the GTM container loading and consent configuration.
Review the implementation of Google Consent Mode v2.
Determine whether Advanced Consent Mode is required and correctly implemented.
Verify consent states such as:
analytics_storage
ad_storage
ad_user_data
ad_personalization
Validate GTM behavior before and after consent.
Determine whether GA4 is receiving appropriate cookieless signals when consent is denied/not provided.
Identify any implementation issues in the CMP/GTM/Consent Mode setup.
Recommend and implement the appropriate fix.
Validate the solution using Tag Assistant, GA4 DebugView, browser developer tools and network requests.
Confirm that the solution does not negatively impact existing tracking for consenting users.
Expected Outcome

We want a properly implemented consent architecture where:
Before consent:
Privacy-preserving GA4 signals can be sent where legally/configurationally appropriate.
No unauthorized cookies or personally identifiable tracking occurs.

After consent:
Normal GA4 tracking works correctly.
Sessions, users, events and campaign attribution are captured correctly.

Overall:
Analytics visibility improves significantly.
Consent requirements remain respected.
Existing UTM attribution and conversion tracking continue to work.
Required Expertise

Please apply only if you have strong hands-on experience with:
Google Analytics 4
Google Tag Manager
Cookiebot or other CMPs
Google Consent Mode v2
Advanced Consent Mode
GA4 DebugView
GTM Consent Overview
Browser/network debugging
UTM and campaign attribution
JavaScript / website tag implementation
Important

We are not looking for someone to simply install GA4 or GTM. We need someone who can diagnose an existing production implementation, identify the root cause, explain the technical findings clearly, and implement/validate the fix.