If HomeRunner is set up to send GA4 events directly to your GA4 property, any GA4 event tags in your agency’s GTM container that point to the same measurement ID fire in GTM’s preview but never reach GA4.
Why this happens. When HomeRunner loads its own Google tag for a measurement ID, GTM does not load a second copy of that same tag. Only one system can own GA4 events for a given measurement ID at a time.
What to do.
- Let HomeRunner send all GA4 events for that measurement ID, including page views, view_item, view_item_list, begin_checkout, and purchase.
- In the agency GTM container, remove or pause the GA4 event tags for that measurement ID.
- Leave non-GA4 tags, such as Meta pixel events and other vendor tags, in GTM as they are.
HomeRunner continues pushing booking events to the dataLayer, so those non-GA4 tags keep working normally.
Adding a GTM exception trigger on the agency tags is a harmless safety net, but it is not required once the GA4 tags are removed.