Troubleshooting
This section covers the most common issues reported by users of Google Tag Manager for WHMCS, how to diagnose them, and how to fix them.
Before opening a support ticket, please work through the relevant guide below. Most issues are caused by one of a small set of known configurations or WHMCS behaviors.
Quick Diagnostic Checklist
Run through this checklist first — it covers the root cause of the majority of issues:
- The GTM Container ID is saved in
Addons → Google Tag Manager(e.g.GTM-XXXXXXX). - The module is activated in
Setup → Addon Modules → Google Tag Manager → Activate. - You are testing on the client area (
/clientarea,/cart.php), not the WHMCS admin panel. The module does not inject tracking on admin pages. - Your WHMCS theme does not suppress
{$WHMCSGTM_datalayer_output}output hooks. Check your theme'sheader.tplandfooter.tpl. - You are using GTM Preview mode (not the browser network tab) to verify data layer events.
- The license is valid. An expired or invalid license silently removes the container ID and GA tracking ID from the module settings. See License Issues.
Troubleshooting Guides
| Issue | Guide |
|---|---|
| GTM snippet not appearing on pages | GTM Snippet Not Loading |
| Events not firing in GTM | Events Not Firing |
| Duplicate or extra purchase events | Duplicate Events |
customerData is missing / undefined in GTM | Customer Data Not in Data Layer |
begin_checkout not appearing | Events Not Firing → begin_checkout |
| Purchase event fires but transaction data is empty | Events Not Firing → purchase |
| Events fire multiple times on page reload | Duplicate Events → Session Queue |
| Module settings are erased after saving | GTM Snippet Not Loading → License |